I first purchased the turtle and the grandkids thought it was fun to try to catch it .  So I purchased the rest of the subbies.  I should have waited as some  flip around better than others but everyone of them gets water inside and corrodes the batteries.  So if you want to constantly  clean battery contacts and replace batteries, these are the toys for you.

I have the penguin version of this toy.  I seriously doubt that it will hold up for any length of time, as it just isnt' quite water tight enough.  Consequently, it eats batteries - I can use it twice (maybe an hour each time) before leakage and my salt pool water finishes off the batteries.

But the kids love this thing.  It doesn't just surface swim, it goes up and down, and bounces off the walls (of course, since I have a pebble pool, it looks chewed on now).  But most important, I have a 4 year old that is a super swimmer.  Now I mean super - she will tread water in the deep end for 30 minutes+ (no idea what her max really is).  She surface swims, underwater swims, and will dive to 5'+.  But this penguin is seriously increasing her swim speed.  Our pool is relatively small, so she tends not to swim seriously.  But she chases this thing all over, and it is a bit faster than she can swim.  In fact, it is probably close to my top swim speed, and I swim pretty fast.

So bite the bullet, buy cheap batteries, know you'll only get 10 uses out of the thing, but expect it will seriously be the best pool toy $ for $ that you've bought in a while.