The game is subtitled Tropical Freeze. It starts out on the tropical Lost Mangroves, as the music and scenery help attest to that, and ends on the frozen Donkey Kong Island, where all the tracks and levels are much more colder in theme.
The sixth world has no levels with underwater segments. It makes sense, since the world is entirely based off of the levels from Donkey Kong Country Returns, which had no levels where you could go underwater. Additionally, with how cold it is there, it’d be too dangerous for the Kongs to swim anyway.
Both this game and Returns have silhouette levels during the first and final worlds. The first one being more tropical (Sunset Shore and Busted Bayou) and the second one being more perilous due to a force of nature on the mountainside (Smokey Peak dealing with a volcano eruption, Cliffside Slide dealing with an avalanche).
Level 6-K appears to be just like any other secret temple in the game, despite being located inside the Golden Temple, first seen in Returns. Where has the exotic, surreal scenery of the temple gone? The reason is because all of DK Island is overrun by an evil force (in this case, the Snowmad Tribe). In the previous game, the temple didn't even appear until the Tikis were obliterated, so the presence of the of the Snowmads took away the magic once again, which is why the temple looks like a frozen ruin.
The first island the Kongs visit is replete with the wreckage of airplanes and ships, and there is an empty diving suit helmet at the bottom of one body of water. What happened here exactly? Was there some Great Offscreen War? Or are these islands in the middle of some Mario-verse equivalent of The Bermuda Triangle (even Funky Kong asks this question in-game)?
It could be one of Funky's planes that, for whatever reason, landed there.
There is a cameo of Samus' ship in one level, and another features a Metroid appearing. Yes, a Metroid.In the Mario-verse. Let's hope that ship means Samus is around there too.
