how do you deter seagulls?

How do you deter seagulls from landing, perching and subsequently dropping faeces all over your boat?
I have tried everything! I couldn’t find much on the Internet and I am praying the collective mind of the straight dope can help.

Solutions offered so far include:
Scarecrow owls or snakes: Didn’t work
Sticky tar: We have to walk on the boat too

Is there a colour, a smell, a frequency of pitch, or a substance seagulls absolutely hate that we can handle?

Your advice would be most appreciated


From paddling around harbors in California quite a bit, I’ve seen lots of different methods, but I’m not sure how effective any of them are in the long run.

Lots of boats had things like this:
at strategic locations around the deck.

There was also this other thing that looked like a horizontal rod with little flags at the tip. The wind blew it around like a helicopter rotor (only slowly) and I guess it was enough to keep the gulls off. I can’t seem to find anything about it through google, but I didn’t look that hard.

On the cheapass side of things, there was someone in Newport harbor that had plastic grocery bags tied everywhere so they’d flap in the wind. I suppose that might have worked, but then, I’d personally rather have some bird poop to clean off than make a $200,000 sailboat look like a garbage scow.