Kelp
The waters off Point Loma in San Diego are rotten with kelp. Sometimes patches of it will break off and drift around in the ocean and into the bay, it's a rare day here when you don't have to dodge some. Any sort of fin keel will tend to collect kelp, I've also had it wrap around the prop and rudder. It's not really the end of the world but it is annoying, your boat speed will drop to nothing. Often you can either reverse under power or spin around a few times to clear it but I've had to dive in on occasion too. Just try to avoid the bigger patches and don't worry too much about the keel design. I suppose a true full keel boat wouldn't tend to pick up kelp there's lots of other negatives to them. Have fun!