I remember reading that water mobs are supposed to be able to locate water sources if they are on land. I decided to try this out when I spawned in a new world that was a small (~30x30) island literally surrounded by thousands of blocks of ocean in all directions.

I first spawned in some fish, wanting to watch them find the water and swim away. But they didn't. They hopped around aimlessly, and swiftly died. The way they hopped around really seemed like random, and there was seemingly absolutely no water-finding ability in there.

Okay, so fish are dumb. But surely DOLPHINS which have a tonne of coded behaviour may be a bit smarter?

Nope. The dolphins were just as bad. They showed no signs of water detection, instead just hopping around aimlessly (with no sound I may add), and even at times, seeming to head towards the water, being within 1 or 2 blocks of the water, then turning around and hopping the other way. Almost as if it was trying to AVOID the water. Dolphins can last MUCH longer on land. It did eventually find the water, but it took MINUTES, and seemed to simply be that the dolphin found the water by chance.

So if this "water-finding" functionality is in place, it's broken. If it's "working as intended"... then wow it needs some serious work.

Guardians actually seemed to have a much easier time than dolphins also, which is very strange as Guardians are an old mob created when the team had far less experience with coding aquatic mobs (and was something they had been actively avoiding up to that point iirc).