To present myself as the counter to an above post, I love the way swimming feels in 64, that rhythm man, you get the timing on the strokes down for that speed burst and it's all like "WUUURP,WUUURP,WUURP"
This is how SM64 can get away with having a side stage that's literally just a cube filled with water.
That said, it's a shame M64's water sections never really do anything interesting out of having some satisfying movement , and I'd be lying if I didn't notice that making smaller movements wasn't a bit fiddly, which probably explains actually why most of 64's water is open space.
Unfortunately Dire Dire Docks is still the worst stage and the ultimate example of how the game does nothing with the water really.
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And a random side thought on Sunshine, it's interesting how this is the only Mario platformer where the abstract is thrown out in favour of creating a sense of place, all the main stages are landmarks populated with NPCs, bottomless pits are rare because they don't gel with the rest of the world design and as such classic platforming is shifted to the FLUDD-less voids, it's such a notable one off in the entire platforming series including 2D Mario.
As I go through 64 and am reminded how many stars are "do what you just did but do one thing different/go left instead of right" I kinda respect how Sunshine isn't nearly as heavy on that with just its obligatory race sections being that same kind of approach mostly.