This could be a puzzling question if you thought that water was going down. Think about it for a moment. Where would the water go? It's already down and everywhere. When you let go of a rock, the water just fills in on the top and moves away on the bottom. It just travels around the rock ... not down. Well, initially, you might get sucked a little while the water transfer gets going (front to back of sinking object). But, since you've presumably held your breath, you should just come up bobbing like a cork momentarily.
Or should you?
Of course, there's more here than meets the lungs. There's a question of
Bubbles are what the big ship can take down with it. This ship sinks with a large supply of air left aboard. It's so heavy, it drags a large amount with it and lets it go as it's heading down. It is the bubbles that suck you down. More appropriately, the bubbles let you "fall" down a hole in the water.
You float in water because you are less dense than the water. When the average density of the water decreases dramatically (as when it's full of bubbles), it's equivalent to a hole in the water into which you can fall.
You can float in water but not in the air. So when you are immersed in what is half air and half water, it's not enough to keep you up. As long as the ship is emitting bubbles you will fall in after it. If you can get out of the bubble stream, you will come up like a cork.
Of course, if you extricate yourself from the bubble stream 1000 feet down, you're out of luck. You've got to stay away from the bubbles right away or it may be too late. Get it?
This reminds me of the transistor where the moving electrons are equivalent to positive "holes" going in the other direction. The bubbles coming up are equivalent to water going down a drain.