I got the Fisher Price Kick and Crawl Aquarium for my son when he was about 10 weeks old or so and he liked it then. He is now 20 weeks old and he loves it!  There are three different ways to use this toy.

The first is as a play mat/gym.  The toys hang above babies head by strong velcro and there is a ball for baby to kick at the foot of the toy.  At first my son couldn't figure out what to do witht he toys but now he can push the button to make the fish play music.  One thing I wish this toy featured is an option ot have the fish play music continueously because my son gets bored and tired...