I've been think about this for a while and it seems to me that gameplay-wise the entire area above the ground - open water and the surface in particular - very much feels like wasted space right now.
The camera being unable to rise above the surface also feels very arbitrary and is kind of annoying, especially since we can actually create surface islands and plants can even grow on them.
So here are some suggestions for open water and the surface.
The area above the surface should be accessible (remove the camera border, it feels arbitrary and we can already trick it in one way or another anyway).
There do not need to be creatures on the land but islands can give resources (food) for the fish. Examples would be special surface plants (ferns, trees) which produce seeds that either drop directly into the water or drift across the ocean (possibly to other islands) before they fall onto the ocean surface somewhere around the island (some may swim onto the surface while others will slowly sink to the ground) or bush-like plants that "produce" insects which can also fall onto the surface and act as food.
Some plants may even drop large chunks of plant material into the water which then drift around as a sort of floating island growing a steady supply of food for nearby creatures until it hits an actual island and the plants set up to conquer that one which will remove the floating island from the water (obviously there needs to be a limit to how many of those floating islands can be spawned so the map doesn't end up covered with those which would probably kill performance on any system).
This would immediately create the resource influx required to keep an entire surface water ecosystem going that may end up almost completely disconnected from the ocean floor with its own foragers/predators (especially when those can actually specialize into eating seeds or insects).
Additional traits like fish being able to lay eggs into the open water or even having live birth would also help to make fish less dependent on the ground level and open up the entire water body for gameplay.
Right now everything above near-ground level feels kind of like wasted space as fish can't find food or lay eggs there.
In this picture there are also a few additional ideas like feeding areas and egg spawning locations as a basis for fish migration and an adapteable system for scavengers.
The camera being unable to rise above the surface also feels very arbitrary and is kind of annoying, especially since we can actually create surface islands and plants can even grow on them.
So here are some suggestions for open water and the surface.
The area above the surface should be accessible (remove the camera border, it feels arbitrary and we can already trick it in one way or another anyway).
There do not need to be creatures on the land but islands can give resources (food) for the fish. Examples would be special surface plants (ferns, trees) which produce seeds that either drop directly into the water or drift across the ocean (possibly to other islands) before they fall onto the ocean surface somewhere around the island (some may swim onto the surface while others will slowly sink to the ground) or bush-like plants that "produce" insects which can also fall onto the surface and act as food.
Some plants may even drop large chunks of plant material into the water which then drift around as a sort of floating island growing a steady supply of food for nearby creatures until it hits an actual island and the plants set up to conquer that one which will remove the floating island from the water (obviously there needs to be a limit to how many of those floating islands can be spawned so the map doesn't end up covered with those which would probably kill performance on any system).
This would immediately create the resource influx required to keep an entire surface water ecosystem going that may end up almost completely disconnected from the ocean floor with its own foragers/predators (especially when those can actually specialize into eating seeds or insects).
Additional traits like fish being able to lay eggs into the open water or even having live birth would also help to make fish less dependent on the ground level and open up the entire water body for gameplay.
Right now everything above near-ground level feels kind of like wasted space as fish can't find food or lay eggs there.
In this picture there are also a few additional ideas like feeding areas and egg spawning locations as a basis for fish migration and an adapteable system for scavengers.
). The main strain on the system seems to come from the creatures themselves, particularly the random misc ones.