Well, this mechanical fishy can be found for about $10. They had two varities, one was a nemo look-a-like (which took one battery) or the one I got which is just a "rainbow" fish (if i recall) and it takes two batteries. I figured that one would swim faster having twice the battery power, hence my decision. Anyway, the fishy's tail flips back and forth propelling him thru the water. He was a little heavy and sank to the bottom, so I opened him up and put some styrofoam peanuts inside (the inside fills with water except the battery compartment). That worked very well except I need to redistribute them so his nose isn't sticking out of the water and tail sinking in. Really not to scary, other than having a battery operated device submerged in water.