Genevosa is the remains of an extinct volcano that is open to the sea on the south side. Sheer cliffs drop into the deep water on the outside, and on the inside boats can enter the caldera and moor in the shallows near the small beach. It is a dramatic and primeval scene! You can dive from the outside of the volcano through the channel into the caldera. The rocky bottom is alive with schools of marbled groupers, jacks & barracuda. This was where I saw a massive school of mantas sweeping past on the surface – there were dozens of them!