You can skip Publix or the local gourmet poissonnerie. Go right to the source. Twice a day, generally at noon and 5 p.m., charter boats cruise in and offer the savvy a chance to buy slabs of fresh fish like dolphin, kingfish, and tuna, often for as little as six bucks a pound. If you want to captain your own expedition, you can usually book a half-day charter for about $200. But why bother when you can just drive up and pick your own tender entrée, still gaping-mouthed and flopping, and have someone else deal with all those pesky entrails?