Something that feels good like this isn't a fetish. It's just something that feels good. (A fetish, long story short, is an erotic focus on an inanimate object.)
It's fine to masturbate this way. However, what's not so fine is to masturbate in public, just in terms of having good boundaries where other people are concerned. Masturbation is something we need to keep private, or only for sexual partners who have consented to be present or part of our masturbation. So, if you're in your backyard all by yourself, that's cool. But if and when other people show up, you need to respect their boundaries and save masturbation for when you have privacy or consent.
Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has. - Margaret Mead