Spot for soft shell crab in South Beach?
Not my area... and NOT South Beach...
But I did see this tempting morsel making the rounds on the web...
Pbuu Hlon - Soft Shell Crab with Minced Pork and Fermented Bean in Coconut Broth by @Chef__Bee
14841 Biscayne Blvd, North Miami Beach, FL 33181
Sakaya Kitchen has a soft shell crab bun on the regular menu.
Hakkasan has a soft shell crab appetizer on the menu - and you'll find them at many Chinese, Japanese and Thai places.
I've had them at the Dutch before but that was probably last spring.
Keep in mind that any place that regularly has soft shell crabs is probably buying them frozen not live - they're a seasonal (late spring -summer) item.