Fort Matanzas was built to protect St. Augustine from British attack via the Matanzas River, which was considered a strategic "backdoor" to the city. Twelve British ships were forced to retreat in a brief skirmish in 1742 as the fort was nearing completion. Today, a Park Service ferry takes visitors to the watchtower fort. During the boat trip, dolphins can be glimpsed surfacing the water. The park is on the only "natural" inlet remaining on Florida's east coast and includes a barrier island refuge.