Dockwalking is the hardest part to finding work on-board any yacht, it can be a demoralising experience, however there are lot of good jobs to be gained from it. Keep going!
Remain professional and smart during your dockwalk. This will help your chances, you have a lot of competition out there. Plus, you never know who can see you.
Never approach the boat when the crew are in formal uniform, this means the owner is onboard.
If you do get work remember this may lead to other things.