To be honest, any spot in Ko Phangan you choose, is probably going to be great for snorkeling. The only difference is an access - if it's hard to get there it's not going to be crowded.
I was there when I was stationed at MCAS Kaneohe Bay in 1966. It was the brightest , and most colorful ocean habit that I had ever seen.
I snorkeled here almost every weekend and I remember the bay water was azul in color and incredibly clear . The bay was easily accessible for anyone who could walk by a long steep stair way of stone steps with pipe guard rails .
Best snorkeling for beginners. you can still see some lovely coral gardens at the south end of the bay, behind the menehune wall. Turtles, morays, humu, puffers, slipper lobster, octopus if you're lucky. Only go to this area at higher tides as you may get too close to vanna at low tide. Please be careful you don't touch or stand on the coral. We love this bay and want it to be protected. Mahalo.
This is a fun snorkel area for everyone! It's wonderful for young children and beginner snorkelers because the ocean entry is easy and you can see abundant fish just a few feet out.I have made several trips here and always see turtles and many beautiful fish. The coral and underwater sea life will not disappoint. If you don't have snorkel gear it is definitely worth the cost of renting it at the stand located right at this beach park.
Ko Ma is like a magic place, fully natural, nearly untouched by humans. Snorkelers are all around it as there are thousands of colorful fish everywhere.