Since he lives there, he will know where to take you. The dive sites are buoyed moorings, they are not just "marked".
Cocoview is in the geographic center of one of the most unusual dive locales in the Caribbean. This zone of the South side presents very shallow vertical walls that run from 0-5' below surface straight down to a 90' sand shelf. This area is situated so that it gets Sunlight almost all day long- the growth and number of soft/hard Corals is recognized to hold a selection of the widest varieties to be found. In this florid wall the careful diver will find the real treasures- it is a nursery incubator for the reef. Colorful juveniles of every kind, Pipefish, little Crabs hiding in plain sight- it is a wonderland like no other.
It is an area best for a more advanced diver: one with better buoyancy and certainly with honed observational skills. It is not the place for divers who are still being amazed at spotting Squirrel Fish or Lobsters. Your friend will likely have a magnifying glass and will be leading you around showing you things you likely had never noticed before.
Snorkeling? We have been to Cocoview many times, and there have been several weeks where we never even got on a departing dive boat- we just did the shore dive off the front of the resort- this is an excellent snorkel.