If you want good snorkeling, you need to go in the morning, early. On two mornings of our vacation we went to Concha Perla prior to breakfast and it was peaceful and the water was clear. In the late afternoon all h..l breaks loose. This is when the sea lions are lying across the path and the locals use it as the local swimming pool. We went twice in the morning and twice in the late afternoon and saw the pattern. You do not need a guide to snorkel here but you do need to bring your own equipment. On one of the mornings I got some photos of an octopus in the water near the pier where you enter the water.