Isla Tortuga is named for the shape of the island, not the inhabitants. The island is a collapsed volcano that is a nesting location for a variety of seabirds such as Frigatebirds and the elusive Red-Billed Tropicbird, among others.
The island is completely protected land so you will not be able to disembark. You can photograph and view the flocks of seabirds, Sea Lions and Marine Iguanas that call this island home from the boat and the water, though.
This tour is a good option if you are a bird-lover or the Lava Tunnels or volcano tour don’t suit your needs.