We have been taking a look at the 10366 Tropical Aquarium, coming out in mid November 2025. This is a large, expensive set, quite unlike anything that the LEGO Group has produced at this scale before. It’s not based on a renowned piece of Architecture, it doesn’t tie in with any preconceived cinematic universes, and neither does it follow up with one of the regular ICONs subthemes. It’s a 52 litre fish tank, filled with corals, plants, and fish of unrealistic provenance. However, I must admit, it looks quite neat. Impressive even.

Fish tanks often feature decorative elements within them. The Tropical Aquarium features a treasure chest, tucked away in the back corner, serving as a bubbler, along with a rock cave and shelf. However, beyond that, it is comprised of all plants, coral, and anemones.

In fact, it’s beginning to look like one of those colourful underwater layouts you often see at LEGO Conventions, with lots of hidey holes and scope for exploration and storytelling. This left me thinking about the broad range of underwater exploration themes that have cropped up over the years, and more importantly, made their way into my collection. And how they could add life to this set.

Let’s start with a quick look at some of the sets which I own (and some that I don’t), which feel as though they might serve as aquarium decorations .

1. A Brief History of Underwater Themes
   1. Aquazone
   2. 1997-2012: Divers, Alpha Team, Aqua Raiders and Atlantis
   3. LEGO City Deep Sea/ Polar Explorers
   4. LEGO IDEAS
   5. SpongeBob SquarePants
   6. The Little Mermaid
2. Let’s consider the space that we are planning to customise.
3. Filling the Aquarium
   1. SpongeBob Square Pants
   2. Yellow Submarine
   3. Fantasy Underwater Layout: Enter the Aquazone
      1. Action Stations
4. In conclusion

A Brief History of Underwater Themes

Aquazone

The first Underwater theme to hit the shelves came in 1995. In fact, it was the first new minifigure theme since pirates (outside the original trinity of Castle, Town and Space). Aquazone had so many of the vibes of being a space theme, that you could probably just remove the aquanauts’ flippers and call them spacemen. Over the 3 years of its run, we had a variety of factions (it wouldn’t have been a 90s LEGO theme without them). Aquanauts were the heroes of the first wave. With their bright yellow Crystal detector and Neptune base, they were searching for crystals that would serve to provide energy for their society. The theme was characterised by the use of octagonal column bricks, some with studs on the side.

The Crystal Explorer came with 2 aquanauts. The submarine has a bulbous front end, with a tranparent blue cabin. The craft had two arms at the front, one equipped with a magnet, while the other had a grappling claw. The prints on the side of the submarine are fantastic, and the cages for the propellors were repeated throughout underwater themes for the next seven or eight years.

Over the years, the Aquanauts had to fend off the Aquasharks and Aquaraiders. The Aquanaut’s successors, the Hydronauts, had to deal with the Stingray faction. Unfortunately, I do not own any complete versions of craft from these factions. That said, the occasional windscreens and propellers (in retina-searing neon colours), along with other theme-specific elements, have cropped up in various bulk lots over the years.

1997-2012: Divers, Alpha Team, Aqua Raiders and Atlantis

LEGO Town had their own Divers sub-theme, featuring research subs, diving bells, support craft and wildlife in 1997. Subsequent Action-Fantasy underwater themes included Alpha Team(2002-2003) and Aqua Raiders (2007). In 2011, Atlantis hit the shelves, launching the theme with a TV special. I collected many of the sets in the first wave of this theme, which included a Red-Bright transparent green craft, as well as a variety of black sea monsters, with increasingly organic forms. Along the way, we had a variety of Anthropomorphic sea creatures: sharks, manta rays, crabs, angler fish, and more defending the lost kingdom from our explorers.

LEGO City Deep Sea/ Polar Explorers

LEGO Town had its Divers. LEGO City introduced Deep Sea Explorer Subthemes in 2015 and 2020, with a few additional undersea sets in 2023’s Explorers range. I have some of the 2023 sets, including the 60397 Deep-Sea Explorer Submarine. The sub has a hemispherical portal at the front, and another window in the roof. The sub has two claws and windows, feeling reminiscent of the Aquazone Crystal Explorer. But with more curves. Also included in the set are a hard suit for deep-sea extravehicular activities, as well as a small drone. There are remnants of a Viking longboat to be investigated, as well as several sharks and jellyfish. The set has a distinctive dark blue/medium azure/bright orange/white colour scheme, like many of the Arctic Explorers city sets. Unfortunately, I fear this submarking might be a little bit too big to mount in the fish tank.

LEGO IDEAS

The final submarine in my collection comes from the early years of LEGO Ideas. No, it’s not the 21100 Shankai Submarine but rather 21306 The Beatles Yellow Submarine. This set represented the launch of many curved elements in flame yellowish orange, bringing a remarkably rounded appearance to the final model. This set comes from an era where a LEGO Ideas set could have fewer than 600 pieces, occupy a small shelf and the box was a work of art in itself. Coupled with the build experience are some incredible internal element decorations, bringing the feel of 60’s pop art to the contemporary LEGO builds, evoking in turn some of the bold graphics of the Fabuland, Scala and Homemaker eras. Oh, and we got minifigure versions of The Beatles.

SpongeBob SquarePants

But it is not all about submarines. Back in the early from 2006-2012 Nickleodeon’s SpongeBob SquarePants had its own LEGO Theme. This coincided with my kids being both into SpongeBob and LEGO Play. As such, a copy of 3834 Good Neighbours at Bikini Bottom is floating around the house. Instant pineapple dwelling. Given that the series is set at the bottom of the ocean, and Sponge Bob Fish tank decorations are in fact a thing, this might be perfect for some people.

The Little Mermaid

I am including this for the sake of completeness, for I don’t actually own any Little Mermaid sets in any quantity. Since they were first released in 2014, The Little Mermaid sets have given us our shares of underwater palacees over the years! There is certainly scope to install Ariel’s Castle in there, near the front left of the aquarium. I am just imagining Ursula emerging from the cave…

Even 2024’s giant shell, based on the live action movie could have some potential in this set, although a major redesign, and significant investment might be necessary.

Let’s consider the space that we are planning to customise.

Here is the 10366 Tropical Aquarium untouched. There is a great deal happening in this model. I’ll particularly highlight the organic shapes in the sand, coral, plants, and fish. Straight edges are virtually restricted to the rock structure and the frame of the tank. In its unmodified form, there are a couple of areas that are probably a little emptier than others, particularly once the fish are removed. The front left of the tank has a few weeds attached to the aquarium floor: they will be easy to remove. The fish are also concentrated on the left, with two occupying the upper left quadrant of the build – it will probably be rather empty with them gone.

Let’s take out the coral, anemones, weeds and fish.

Here is the Tropical aquarium with most of the coral and weeds removed. I have left the orange anemone and treasure chest in place, as they are firmly integrated into the model. The purple anemone is a little harder to remove, but my early experiments made me think that it could be useful to clear this space as well.

Filling the Aquarium

So, I raided the household collection and found a few underwater examples from the Rambling LEGO Cupboard…

SpongeBob Square Pants

Probably the simplest customisation is to install the pineapple from Bikini Bottom in the front/left quadrant of the tank. We might need to move a couple of the sloped bricks from the tiled area, to allow the pineapple to sit easily. If we are going to feature Spongebob’s home, why don’t we treat the cave as Patrick’s garage. We can keep the fish in the tank, but let’s add some ‘splat gears’ in purple and azure to mimic the flowers seen in the background on the TV series. Let’s get Squidward to recline on the lounge, passing the day away. With all of this decoration at the bottom, there is probably no need to move the fish. There might be scope to install 3833 Krusty Krab Adventures on the rock shelf, but since we never owned that set, the topic is somewhat moot.

Yellow Submarine

I thought it might be fun to adapt the Aquarium so that the Yellow Submarine could be supported on the oscillating pole behind the rock shelf. However, a few changes might need to be made: Let’s lower the pole, so that the submarine is not cruising above the water level. The other challenge comes from the angle of the turntable. It almost ensures that one end or the other will repeatedly hit the back wall. I inserted a longer arm, along with a spacing connector, to rotate the turntable a little closer to east-west, and less likely to collide. We can place the band down in front, as well as the placard. This got me wondering about the other great underwater Beatle’s song: Octopus’s Garden. So I threw together a small octopus and put him on the slider in the cave.

What do you think?

It’s not without its limits – in particular, the submarine bumps into the wall and anemone as it sways back and forth.

Fantasy Underwater Layout: Enter the Aquazone

I spent a bit of time considering which era of underwater fantasy theme to use, based on our personal collections: Aquazone, Alpha team, Atlantis or LEGO City. Ultimately it was Aquazone.

Let me explain why:

The 10366 Tropical Aquarium is a brightly coloured set, filled with organic forms, in a wide variety colours (mint, purple, spring yellowish green, reddish-orange, dark red, lavender and more).

While the Alpha Team Deep Sea sets used bright yellow, and transparent brown/(old trans black), the previous Alpha Team wave was mostly black, with a little yellow trim and transparent blue. This was also one of the first themes to embrace curved slopes in the construction. As it turns out, I only own a copy of 6774. I’m not sure we would have had enough action if I just used that. I don’t seem to have encountered any of Ogels vehicles or base in lots that I have picked up over the years.

By the time Atlantis came along, curved bricks were de rigeur for construction of spacecraft and submarines. The grey, transparent green and red are all fairly similar to colours already featured within the Tropical Aquarium’s rocks and weeds.

The 2023 City Explorers Submarine appeals to me a lot, but it is covered with smooth curved, in orange and azure: While the colours and form may lead to it being hidden in the Tropical Aquarium, the submarine is just too big in the layout.

Aquazone is full of bright yellow, blue and black, as well as transparent blue; transparent neon orange and transparent neon green. The stark angles of the Aquazone craft contrast well with the rounded nature of the corals, anemones, and plants.

I had a few Aquashark elements – specifically the propeller cover, and a windscreen, so I put together a small submarine. I had hoped to fit it in the cave, but unfortunately, there is very limited space. I decided to made a very small, crab-shaped vehicle, using the windscreen element used by the Sting-Rays. A small Aquanauts scooter sub left me feeling that I had made some sort of an effort here.

In order to fit the Crystal Explorer in the tank, I removed the large lavender anemone and tucked a few bricks under the submarine, resulting in a somewhat jaunty angle. I placed the Aquashark sub on the oscillating pole, and the Crab sub on the cave slider.

I borrowed the great white shark and jellyfish from the LEGO City submarine and set them up around the tank. They are, however, somewhat static.

I added a couple of Aquanauts divers and a somee Aquasharks, racing to get the silver crystals. I used some of the transparent bars, as well as the ‘super hero’ handle with stud to give the feeling of divers swinging into action.

I like the idea of having an underwater civilization fighting off the human miners, of either faction, so I rummaged through one of our older boxes of minifigures and found some of the shark people from Atlantis. Add in some tridents and supports, and they are ready to defend their home.

And this is where the Tropical Aquarium Springs to life.

This is, for the time being, the best I can do with the tools (and parts) at hand.

The Tropical Aquarium becomes a home for the Aquanauts and Aquasharks, with different craft vying for position while their divers dodge opposing teams in the quest for the silver crystals.

Action Stations

We preserved the action features, with a diver trapped by the anemones, the Aquashark Submarine turning on the pedestal, and the Crab Submersible emerging from its cave. With a little more thought, I might cannabilise the mechanism from the treasure chest to move the small yellow craft.

With a little more thought, I might cannibalize the mechanism from the treasure chest to move the small yellow craft.

In conclusion

So there we have three different reimaginings of the LEGO ICONS 10366 Tropical Aquarium: SpongeBob, Yellow Submarine, and Aquazone. I probably had a little more fun doing one of these over the others. And you can probably pick which one it was. Which was your favorite?

Still, it was fun to get out the Yellow Submarine, which had been waiting for an excuse to get built. So was the Crystal Explorer, which I picked up at a flea market in Denmark a few years ago. The SpongeBob version had both of my kids saying, “Hey Dad, I loved that thing you did…” And if that isn’t high praise, I don’t know what is!

At the end of the day, I just wanted to put forward a couple of ideas for how you might adapt this set. I could also consider ‘The Little Mermaid’ as another way to do up this set – but my personal interest (and parts selection) is just about absent. If you go this way, let me know.

Now, I don’t want you to think “Wow, this is great, I want to show off my LEGO Divers from 1997.” I’m working to convince myself about the value proposition of this set. No matter how you spin it, this set is expensive: $AUD699.99/$USD379.99 is just a lot of cash, whether it is great value for money or not. This will be the subject of my next article about this set.

Say what you will, this is one of the few LEGO ICONS sets released in 2025 that is not a continuation of an ongoing series (Modular buildings, Cars, Spaceships) or a licensed property. It is a bold and courageous set to bring to the market: certainly one that caught us by surprise when we first saw it revealed last month.

I probably would not have bought the Tropical Aquarium on spec, but since it was here, I have to admit that getting out the Aquazone was more fun than I expected. Personally, I find it hard to customise the appearance of sets, at a visceral level. Even more so when those sets are a significant financial investment. Ten-year-old me is very disappointed!

The Tropical Aquarium polarised opinions when it was revealed. Do these reimaginings /extensions /customisations change the way you initially felt about it? Leave your comments below.

The 10366 Tropical Aquarium has 4154 pieces and will retail for $AUD699.99/USD379.99/ €449.99 / £399.99. It is available for preorder now, and goes on sale in mid-November 2025.

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Until Next Time,

Play Well!

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Appendix: Additional Video Content

We have made a couple of additional videos exploring these transformations, which you can find on our socials…

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