Chuck's right. The kelp is the result of the reef; it won't grow in sand. The tides and wind have some effect on the beach break, but the real driver is the steepness of the beach. As the surge retreats and meets the next incoming wave, a nearly vertical wall of water is formed. The resulting wave then breaks again, rolling everything in its path. The video will clearly show this phenomenon. When I was there a couple of weeks ago (when the storms were coming in), this wall of water was about eight feet high.
This is not like the "normal" or So-Cal beaches where the surf seems to break on top of the water surface. I've dived there and was taught to tuck your head into the wave as it approaches you and it works well. If you tried this at Monastery, the wall of water would simply overwhelm you.
The reefs north and south of the main beach diffuse the wave energy enough to reduce this tendency. The middle of the beach has no reef and the wave's energy is more focused. This is the most dangerous way to enter the water and offers nothing but a long surface swim to the reefs, yet I still people entering in this area.
