The skills to be demonstrated are most of those done in a pool. They include,at depth: partially flooding and clearing a mask, removing and replacing the mask, doing a share air with a buddy exercise, discard and locate regulator, demonstration of buoyancy control, a very basic navigational swim, a controlled emergency ascent, etc. With each dive is a "tour", just diving and getting used to it and excited by it. There are also surface skills regarding setting up equipment, removing and replacing equipment and weights at the surface, snorkel-regulator exchange, navigation swim, tired diver tow or push, buddy check, weight check, and etc. Most importantly the 4 open water dives offer the student a chance to to demonstrate and improve the fundamental skill of buoyancy control and body control in the water, and to have an initial "real scuba experience" times four under the watchful eye of a professional. To learn more, take a certification class. I highly recommend it!
DivemasterDennis