Don't listen to the below. You did the right thing with those crabs. Dropping them in boiling water does not kill them instantly and can taint the meat. You can also use a cleat on your boat in a pinch(makes a bit of a mess) or grab the back flap, slide it up, push your thumb in and pull the top shell off, but that takes practice. Like Dale said, grab the back legs or by the back, they're back legs can reach you but not the claws.
you really didn't bash them on the beach right?? you were joking?? Boil a big pot of water once boiling put the crabs in back side first. Kills them almost instantaneously. Boil for about 20 min and they are done. Have fun I'm jealous.
skully hawk we actually used a hatchet . It was quick and painless. we never had a big enough pot to boil them all whole . We did find that we wasted no meat with the hatchet method.got the idea actually from watching locals clean the lobster in Anegada BVI'S.