If sailing is something that she enjoys because its doing something with YOU then sure, sailing stuff for xmas is always fun. If she does it JUST because it makes YOU happy, then it may not be the best idea to get her sailing stuff. In other words, if she's the one constantly badgering you to go out sailing with her, get her sailing stuff, but if you're the one that's like "hey hon, why don't we go sailing?" and she says that she's too busy because she has to wash her hair, then maybe getting her a nice trap harness for xmas ain't the best.

Alternatively, you could do what I did, and get her nautical/sailing styled jewelry. It can be hard to find stuff that looks nice and isn't tacky in this area, but it does exist.