Some ideas:
- Dolphins
- Squids
- Water currents
- More whales, maybe different types/sizes
- Kraken
- Some form of water dungeon
- More ocean specific localised resources, like driftkelp
- Storms and tornadoes
- Pirate ships
- Turtles
- Fishing boats with castable nets attached
- Ice bergs
- Sharks
- Manta rays
- Albatrosses
- Pelicans