i think waves could be a good addition to the oceans because rn anyone can go anywhere over the ocean in a vanilla boat i think waves should do damage to your vessel if they go onto a deck and if it completly submerges the boat it should do twice as much as a wave hitting the deck. sea monsters would also be a good idea where you could use cannons to defeat them or use any weapon but they would eat vanilla boats and players whole. they would various things depending ont he zone a coupl ideas i have is sea serpents, sharks, hydra, charybdis, kraken, or cthulu but the last one would have to be summoned and would drop like 5 runes or smth but be extremly hard to beat. they al lwould drop 1 or multiple useful items and would be in different depths, the shallowest being the shark which is just a small inconvience which has 15 hearts. the sea serpent would be next having 30 hearts and taking out vanilla boats in 2 hits. then would be hydra having multiple heads with 30 hearts each and it would take out vanilla boats in one shot, charybdis and cthulu can 1 shot any craft under 1 thousand blocks but need to be summoned in the deepest ocean kraken could take out wooden ships in 1 shot but not do much damage to other ships