Can Fish Tycoon be purchased in stores or just online? I would really like to have it but I don't have a credit card.

You can buy the game using PayPal. Here is the link
www.ldw.com/ft_win

If I use paypal will I get the game immediately or does it have to be sent by mail?

The game can be downloaded using the link that Carla provided, and you can start playing it in trial mode immediately. When you purchase the game, you will be sent a registration code that allows you to continue playing the game beyond the trial period.

It also comes on some new computers. that's how i got hooked!