Does the gift have to be given at Christmas? I'm not familiar with your area but how about setting aside the money and planning a weekend trip to a big boat show? Hotel room, two days to linger over boat stuff to touch and see, soak up the atmosphere that surrounds boat shows, attend seminars. Sometimes if you go on the last day you can get bargains for the stuff the vendors might not want to schlep back home.
I like the sailing lesson idea, too.
Oh, does she have her own knife? Something she's comfortable using in an emergency and is a good grip for her hands? I've heard good things about and am trying to decide on a Kershaw knife for myself.
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