Thing is sooo hard to see as it's only about 1/8".
I don't think it's a Mantis as I don't see any rear 'legs', although it does swim with it's claws tucked under. All I see are black eyes and a transparent body at this point.
It has 4 antennae and a split tail, like a typical food prawn/shrimp.
Guess it could be anything at this point, huh?
Sure would be nice to get a worth-while hitchhiker
