http://www.amazon.com/Alfa-Wireless-Original-9dBi-Strongest/dp/B001O9X9EU/ref=sr_1_3?ie=UTF8&s=videogames&qid=1275072414&sr=8-3

The only way you can do any better than the Alpha is to go with a directional gain antenna.

You don't need height unless you're in a marina and being blocked by a neighboring boat. It's not as if you're trying to look over the horizon with these things.

It's not waterproof -- so keep it sheltered by your dodger or bimini. You can get a 15ft. USB cable.