It would be really nice if the underwater world would be improved upon. It's such a shame our underwater nichelings are just roaming a mostly barren world.
Here are some ideas I have thought about:
*Underwater biomes that correspond to the island.
*Underwater predators of varying strength.
*More underwater prey.
*Underwater permanent nests.
Here are a few examples of what I'm thinking about:
*Warm islands would have oceans with lush, colorful coral reefs with tough shark-like predators and some type of smaller predator, like piranha or electric eel. Several types of hard-to-catch prey items, like fish and the like.
*Oceans around cold islands would be more barren with tough orca-like predators and smaller seal-like predators. Prey items would be fewer and far between, but would maybe be easier to catch.
*And finally oceans around temperate islands would be somewhere in-between the warm and cold oceans. There would be more rocks and seaweed everywhere instead of coral reefs. I don't have any specific ideas for predators, but a different type of whale or shark predator could probably work or maybe a sea lion or something like that. And then a moderate amount of prey items.
*Permanent nest would be scattered similarly to permanent land nests.
These are just my suggestions. The oceans could easily be different if other people have better ideas, I just really wish there were more to do under the sea!
