I've played around with SeaClear on a notebook computer connected to a GlobalSat MR-350 GPS receiver. But because of the size and lack of weatherproofness (is that a word?) I've not used it in my cockpit underway. Rather, it stays below for course planning and as a backup.

Two ideas I've had but not pursued:

(1) Leave the notebook below but connect it to a mini-monitor in the cockpit. A 7" or 8" LCD mini-monitor can be had for $100-$200. One I've seen advertised is connected and powered by a USB cable. The low cost mini-monitors are not waterproof but there are more expensive ones that are. Perhaps couple that with a flexible waterproof keyboard for input from the cockpit.

(2) Get a used Toughbook notebook that meets mil specs. They're supposed to be moisture proof, perhaps even waterproof. The size problem may still remain. Or there may be a way to get a Toughbook monitor and connect it to a notebook kept below.