A straightforward premise with a surprising degree of complexity! I really like the idea behind this one.
It did feel a little painful having so little control over your fish - in particular, I really felt dependent on the few that could move vertically. On the other hand, finally cornering the dang UFO made me feel much more clever than I deserved to!
My one nagging thought is that the game might be more fun with multiple UFO's to pursue - maybe I just like clicking a lotta stuff at once, but I feel like that chaotic energy would be a lot of fun!