~My ideas~ :
Simple Ideas :
-Auto-save
-Way to have back your world (like you log in but your inventory is empty , this will get users use chests to retrieve their stuff)
-An small tutorial mode
-Sharks can grab your hook or fishing rod if you throw it close to him
-More animals
Advance Ideas :
-Multiplayer worlds (Private servers)
-Community help in game (other than itch.io)
-Online world submiting (people can see creations from the community , with list from biggest world to more resources)