Just a post to share some ideas I have that could really spice up the ocean. I’m sure the devs have already thought of some of these.
Whales-Can be killed for their meat as well as their blubber. Potentially even whale skin could be used for a suit that increases swim speed and lowers stamina use while swimming. Whale blubber can be used to turn into an oil to fuel torches/sconces as a replacement to resin. Would last much longer.
Hunting Ship/Whaling Boat-Either a new boat or a Harpoon attachment for the longship. Attachment could work similar to crafting station upgrades. Whale Harpooning and Serpent Harpooning would be done through this system and allows Vikings to haul them to land without using stamina from the abyssal harpoon.
New Fish- Various fish that can only be caught while in an Ocean Biome. Swordfish would be a cool one. Could unlock a new weapon. Electric Eels could be caught with abyssal harpoon on shores or shot with a bow. Adds food plus some item that is used for lightning damage.
Ghost Ships- Floating boats with dead sailors aboard. Could be Draugr’s or a new enemy. Can find treasure on them as well as some unique items, maybe for boss summoning.
Lobster/Crab pots- Allows for a way to farm chitin slowly seeing as it will be used for many new items added with this content. Leviathans will still be used for large hauls. Maybe yields 1 a day per pot.
The Ocean Boss- A monster that lives in the center of a whirlpool. Boat is locked in spinning around it. Scylla and Charybdis vibes.
The ocean doesn’t need to have it’s own tier of ores because then it would become irrelevant once you beat that tier. Rather the ocean should be relevant throughout the entire play through, yielding materials that can be used at every stage of the game. Maybe once you beat each land boss it allows for new creatures to become spawnable in ocean. This is a viking game and I think the ocean should be relevant for the entire game. Constantly a reason to go out there and kill and harvest materials. I think the ocean boss should probably be the final one. Everything you do builds to that point.
Edit: Thank you all so much for the incredible feedback and responses. I wasn't expecting this to get any attention, just wanted to throw some thoughts out into the forums and maybe give a few people some ideas. You guys are all incredible and it goes to show how wonderful and passionate the Valheim community is!