Yep, what Chagy said. Those are on modern charts also. They represent either exposed area at low tide or very shallow area at low tide, usually with rocks. That coast has some shallow reefs and sandbars North and South of Sebastian Inlet. But what Peg Leg said about some of the wrecks being under the sand is true. Some of the wreckage is under sand on land. Either the boats unloaded all the ballast and heavy cargo, and rolled up on the beach and later went below the sand, or the shoreline has moved out, onto the wrecks. I follow the latter theory. A well documented wreck on land is the 1715 wreck that is called Corrigans (for the original homebuilder) that is under the sand. There was cannons dug up when they were digging the foundation for a house in the 1940s, and then when they built the condos that are there now, they had lots of artifacts come up with the digging.