Found myself in a Deep Ocean biome for the first time, and it's honestly kind of scary, swimming at the surface, looking down, and not being able to see the bottom.
They need to add ocean-going hostile mobs now, just so you can get the experience of having a great white shark come rushing out of the depths, or even just see a faint hint of movement down there, and start fearing for your life.
And once they add hostile ocean-going mobs, they need to give you an update or two to wait and be afraid of the water..
...and then they need to add a bigger boat.
Anyway, great whites, giant squid, and maybe a couple of other nasties would really make the oceans more fun.