If you can manage to wait until fall, Otter season opens on November 1st in Washington. You can rid the marina of pests, be a hero to your fellow boaters, and pad the "cruising kitty" a bit. http://wdfw.wa.gov/publications/00769/wdfw00769.pdf
Okay, so that probably isn't in your plans. Just an alterntaive!!!
Good luck with your project.