Ceviche is to South Florida what ice cream is to the rest of the nation: a refreshing, warm-weather treat that comes in so many flavors that Baskin-Robbins is blushing with envy. There is tuna ceviche with crabmeat, shallots, jicama, and black beer sorbet at Ola on Ocean. Salmon with watermelon, sprouts, avocado, and chilies at Chispa. And Cacao wows with chunks of Mexican guachinango fish and poblano peppers. Still, sometimes chocolate and vanilla are more satisfying without the cookie dough and bubblegum, and Captain Jim's basic ceviche of raw corvina marinated in lime juice with red onions and cilantro is apt to satisfy a craving for this traditional Peruvian specialty in a way the others won't. Jim Hanson's Key Largo fleet catches the fish for his own restaurant as well as others in town, so the ceviche is always superfresh. Inexpensive, too ($7.99 per pound). And it won't melt in the Florida sun.