Yes, indeed. But I'd rather have things to look at out of my gigantic underwater dome before spending the time to build it.
I'm sure that Notch will probably make some more underwater mobs or objects in the future. Someone made a coral reef mod, you should look into that if/once the Scuba gear comes.
Also, there's this trick where if you have a bucket underwater and you're low on air, you can right click in the water a couple of times quickly and you get full air back. There's your scuba gear rite dar. C: