The only beachcat I ever heard of being actually hit was Sue Walsh's at the Rudder Club in Jacksonville, FL, about 1970. Her Hobie 14 was hit on the river. She sailed in all shook up. Spectators went to look at the boat as the mast fell down- the bow bolt holding the split forestay had melted thru the fiberglass. No apparent damage to Sue.

See many scientific references at http://www.lightning.ece.ufl.edu/
The University of Florida Lightning Research Lab Prof. Martin Uman (also Dr. Ian McEwen now retired), have given lectures to sailors on this subject: Grounded sailboats get really badly damaged (pinholes and blowouts) unless there is a huge grounding plate attached thru the hull. PS: Do NOT run across Florida waters in a speeding powerboat with many lightning rods sticking up (otherwise called carbon-fiber fish poles). Many deaths result yearly from this.

PPS: Carbon masts explode- near the top? I saw a new Viper that contacted a powerline in the 2008 Mug Race at Palatka parking lot. Exploded a softball sized hole at point of contact.