I can't vouch for the product, but here's a site, which has some chart-ware that is freeware:

http://www.sping.com/seaclear

What are those golden rules....??? One hand for the boat and one for yourself.... Never use the life raft unless the boat leaves you ... and ...... when navigating, use what ever electronics (or chart-ware) you wish, but always rely on hard data you can see and verify for yourself.