If your friend hasn't stipulated what he or she actually wants, you may both be in for an embarrassment. People with boats can be very picky (a place for everything and everything in its place!!! ).
This is me. When someone gives me a physical gift it's basically something that makes me artificially smile, take, and then throw in the trash when I get home. I appreciate the gesture, but it's just wasting money and adding to a landfill. I'd rather they didn't give me anything, I really don't have the room. But you can't really tell people that and not offend them
If I really needed to give a gift to a cruiser I'd find out if they had a Kindle or iPad. If they did, they'd probably love a gift card they could spend on either(ebooks, music, etc).
But physical stuff... land dwellers don't get it. Heck, my sister gave me a bar of soap and my boat isn't setup to where I can use bars of soap