Could it be possible to have items trashed in the oceanic tiles either float away, somewhat akin to how items are trashed on space platforms, or even sink into the sea after being dumped? Just something that gives a bit more visual feedback to deleting items in this manner

I've actually implemented something similar in my mod, Dispose in Liquids. It adds a particle effect when an item is disposed of, with the particle color depending on the liquid it's dropped into. Feel free to give it a try if you're looking for a bit more visual feedback.