OK - I just have a little Bravo - but I was SO sick of the gulls perching on Baby Bob and cr@pping on my boat/sail all summer
Winter is approaching and the boat has been pulled in from the lake. But while it's disassembled - I decided to give Baby Bob a makeover. Meet Fierce Bob:

I just used fast-drying craft enamel for the paint - I picked yellow for the top color since I read somewhere on this forum that someone had noticed that the gulls didn't roost on yellow kayaks. And I like yellow anyway

Other folks have used "eyes" to keep birds out of their garden - so I added those AND teeth. The spiked plug is 2" of 3/4" PVC; a coupler; another short piece of PVC and a cap. The "spikes" are pieces of heavy duty nylon "weed whipper" material dabbed in PVC cement.
I won't know until next spring is this actually works - but I can't see how a gull could possibly land on this (or would want to?)