Egmont can be seen from Fort DeSoto if you can't find a boat to take you out.

As far as Sea Horse Key (Ceder Key), from a boat you can see just the very top of the lighthouse. Also the island is off limits the first four months of the year due to birds nesting. Also if you manage to get on the island, there are rattle snakes...that said I never saw one the 3 times I have been there, but I make sure to make noise as I walk. It is open to climb one weekend in October for the seafood festival and boats make runs to the island.