Shoaly You Can't Be Serious! started life as a gamejam entry (available for free here) and was developed into a more complete game, with extra music tracks and SFX added, but more importantly lots of flexibility in how the game plays (difficulty - as in the number of sharks / nets / electric eels you face) and fish density (how quickly the fish populate) were incorporated. There is also an endless mode, the chance to just chill out and watch a virtual aquarium, and an extra enemy to deal with (jellyfish).
It's designed to be a challenging yet relaxing game - so while you will need quick reflexes, the two-player game gives you a combined score, if you want bragging rights that's up to you but the game …doesn't assign a winner and loser! Part of the reason for this is that my youngest daughter was my chief play-tester. ;)

As you can see from the screenshots the game area can be quite serene or completely manic, it's completely up to you!