Ben, you are correct, these are advanced dives, you and the boat crew need to know what they are doing. Most of the dive shop will not even consider taking any one. 3 years ago I heard about Arrowsmith and my good friend Kiki (Enrique's Unique Dives) was willing to arrange it, he grew up on Isla and had never been either. We hired some spear fishermen to take us. One lead us, the other hung on to the boat in the water, with mask and fins telling the boat captain were we were at all times. Any time we looked up, from 100 ft., they were above us.
Last year we did Picos, on the way out we saw hundreds of whale sharks. The dives were deep, 150ft., saw bull shark, 2 big black tips and 1 hammerhead on the surface kind of. The spearfishermen said there was one, I grabbed a mask, dove in and saw a tail swimming away. They thought I was crazy.
I know Sammy, who wants to go. He is a dive master and a great diver, I have dove with him before. Anyone wanting to do these dives needs to be experienced, no just have an advanced card. These are deep deco dives. No room for mistakes. That said, they are some of the most awesome dives I have done.