Does anyone have a good small wrench recommendation that doesn't rust for on the water adjustments?

We have been using a large adjustable crescent wrench which is heavy and doesn't stand up to salt water.

I am not sure of the exact size and my internet searches didn't turn that up. If you happen to know or have a wrench that is small and light and you feel comfortable leaving in the tramp pocket, please let me know the size and model. Thanks!