I always really loved the Atlantis theme, I have collected most of them, not this one though.
I finally got the Portal of Atlantis set from a guy in the forum almost ten years after it was released, but I still have not been able to find the City of Atlantis for a decent price, probably because the last line was limited edition:(

Atlantis!

I fell in love with this set as soon as I saw it. IIRC, it was hard to get in Australia, it was a K-mart exclusive. But for me, this was the very best Atlantis set, bar none.

It has everything! Freaky giant sea-monster and an underwater tank that stands up and turns into a giant robot! I was in love.

I was lucky enough to get couple of them. I especially liked the creature designs in them. So cool, so ferocious.

@Harmonious_Building said:
"Underrated theme...from the guy who was never fortunate enough to own any of them =( "

I know. Just like you. I always thought they were worth getting, but the only one my household owns is a tiny Atlantis poly bag. Guess you can’t always have your way :(

Man this looks awesome. I've never seen it before.

It does crack me up that he goes exploring the deep sees with a rocket launcher. That fish had better look out!

I got this and a few other Atlantis sets off eBay a couple of years ago! The Neptune Carrier is definitely my favourite, though this one comes a very close second.

How well did the transforming function actually work with this. Images make it look like it folds it’s legs around a little clunkily

Love the tail piece of the creature and those wheels in red are cool!

@Brickalili, pretty well. The set’s page has a good number of video reviews which are worth a watch to see the transforming function. It’s a sweet rover.

Makes me sad never having gotten an Atlantis set. This theme was seriously cool

Ah the Mech that Atlantis borrowed then never gave back, would have been cool to see this as a power miners mech!!

Finally! The first RSOTD that I own!
Atlantis was such a great and underrated theme, easily one of my favorites. I have so much nostalgia for it!

One of the few themes that used Trans Bright-Green as prominent colors.

Even up to now, other themes using it were mainly Hero Factory, and 1 wave of Nexo Knights.

Bought the smallest set from the theme, really liked the sets and the theme!

I was still in my Dark Ages at the time but was lucky enough to get an 8075 Neptune Carrier a couple of years ago MISB via BL for just 19 Euro. Have still got it sealed but plan on building it someday. Looks so cool.
Brilliant theme overall.

I missed this theme as I was also in Dark Ages.

But if you combine those white airtanks (from the astronauts with golden visors) with the trans-lightblue/orange visors from 2019 City Space, you can make new Atlantis-like divers with current sets, just different color equipment.

Add the 2019 Underwater Robot and Deepsea Creatures for some more :D

Not saying that it would replace the theme but still fun possibilities.

I do like the Portal and City of Atlantis sets the most but I'm biased toward locations.

Well timed! I just built the Neptune Carrier last night. It really surprised me how much the sticker material has improved over the last ten years.

Love the mech design just by itself.

My favorite Atlantis set !

I never got into Atlantis (not a huge fan of underwater themes). Looking back, though, some of the sets were pretty cool. Kinda bummed I passed on this theme...

Can't believe even Atlantis is a decade old now.

Atlantis was one of the best themes. Best submarines... the Atlantis creatures was sadly a bit underwhelming... The oversized sea animals from AquaRaiders (2) was amazing there. Something went wrong when the first wave Atlantis was released. The second wave picked up the nice creatures.

This was my absolute favorite Atlantis set as a kid. It's only half assembled now because I haven't gotten around to fixing it, but both models were superb in detail and playability. LEGO doesn't do near enough sea serpents.

Atlantis had some great builds, but the theme sold like liquid ass. I was stockpiling D2Cs at the time (Green Grocer and Fire Brigade, also some Imperial Flagship) and people with Lego to sell would call me and ask if I wanted any Atlantis, and I always had to say no. Smart call.

I loved how LEGO managed to make a nice shared Univerves between this, The Egypt Explorers, The Monster Hunters and The Aliens themes.

Ooh love a bit of Atlantis! I was just emerging from my second dark age when it was about. I didn’t have this, but I did have gateway of the squid and a few smaller sets.

@namekuji:
If that's truly the case, my money is on whatever fish-thing Blacktron bio-engineered to take it out.

@BionicleJedi asked "have they visited that kind of environment again since then? If they have, I don't remember it."

There was a Divers subtheme for City a few years back. Turns out it was actually called Deep Sea Explorers. It's more realistic than Aquazone or Atlantis, but it does at least have submarines. https://brickset.com/sets/theme-city/subtheme-Deep-Sea-Explorers

I wasn't into the theme when it came out. Years later, a relative found me a couple of the smaller sets at a yard sale. Now, I have almost collected them all.

@BionicleJedi said:
"Sounds like about time for Lego to revisit to underwater themes again soon..."

City gets another Ocean Explorer theme this summer 2020.
Also a Hidden Side Submarine set.

2019 : Friends Ocean sets are still on shelves, alongside City Diving Yacht, 3-in-1 Underwater Robot and Deep Sea Creatures.

And as I posted before, if those helmet style was desired, parts from 2019 City Space can be swapped to make those diving suits , with gold, lightblue or orange visors.