Currently, the ocean biome consists of, well... water. The only thing that spices it up and functions as a means of landmarks are the small islands that sometime spawn throughout the ocean. Currently, they seem to have been a hastily programmed feature of the game, with messy piles of dirt and oak trees. Yeah, oak trees -- on tiny, seemingly tropical islands. All I'm suggesting here is that the ocean islands need to be reworked. This would not require too much effort on Mojang's part, but would help smooth out the unpleasant bumps in the game.
Simply put, (keep in mind, this is just my personal opinion) the islands need to be flatter, never more then 3 blocks above sea level, and have more sand. Islands are chunks of land just above the water, with the waves pounding their edges daily, and it just doesn't seem right to have so little sand to so much grass and dirt. In addition, I perceive that the idea of palm trees and perhaps cocoa-bean-like coconuts would be a reasonable request.
Finally, with all the treasure chests being added to the game in lieu of desert/jungle temples, dungeons, strongholds, villages, and abandoned mineshafts, it would seem that adding some rare gold-containing chests on the ocean islands would fit the theme of the game and where it's headed. Anyways, it would also give reason for players to venture out onto ocean biomes, as they are probably the least popular and least explored biome in terms of surface exploration.
Also, fishing in an ocean biome should have a small, perhaps 20% chance of giving you a larger fish then the current "fish" item.
If you got this far, then thank you for taking your time to read this and feel free to add your thoughts to this topic.