I love it.
This game is so much fun. Here are some tips for you guys:
Techniques:
This game is basically reverse dog-fighting. Wait for the enemy to get behind you, then hit em' hard. Fly toward your enemy and dodge at the last second with an acid burst and they will probably turn, and fly into your acid. Bam, dead.
Anti-Piranhas
Swim for the surface, then jump out of the water and button mash the acid, propelling yourself. You won't fly up, but you will move down super slowly, killing enemies below you! As you fall into the water, immediately head straight down, and zoom past the remaining enemies, shooting as you go. This is the easy technique for dealing with Piranha swarms.
Unlocks/Achievements:
Pearl Body: Giant clam along bottom of Ocean
Using the Anti-Piranha technique above, you will get an achievement!
Hope this helped