I am somewhere in Florida in a gulf city and trying to reach the beach. Looking at a map, I see that most roads lead toward the water, but that only one or two actually pass over causeways directly to water. Next am in a small boat in one of the bays between the beach keys and the mainland. I drop a flat, yellow plastic box in the water by accident and it sinks. Then boat suddenly touches bottom. A shark flashes by and then turns back and heads for boat. To say the least, I am frightened because boat seems stuck.