complex programming? uh...iono about that...
add some soft background music
make other kinds of bubbles you can pick up.
small ones...big ones...medium sized ones...
and not only can you just have a bubble that slows down time...
you could have one that's a temporary invincibility thing.
another that gives you another life...
tons of things.
you should have also made the fish do something too.
and maybe a time limit to show how much time till you get to the surface, or the next level where you would see a new kind of fish or bubble.
when i make stuff...i try to add tons of variety.
you'll notice the amount of weapons you can pick from in SS2...the obstacles in Tanks...