Mai Ngam beach on North Surin Island is truly an amazing place!
Strongly suggest that one avoids booking the 1Day trip to Surin island,
in order to avoid the crowds of day travelers from Khaolak & Phuket.
Instead, choose to spend a minimum of 2Nights on the island, staying in either the national parks bungalows, or the national parks tents.
We have stayed in the tents for three times now, (the 3rd time being this April'18). Of course the tents offers very basic accommodation, with shared communal toilet/bath facilities, and added to this is the poor service quality of the national parks staff...but the natural surroundings make it all worth the stay.
The view & setting of Mai Ngam is spectacular! You can swim right off the beach with crystal waters and witness some small fish & coral life. The best snorkeling is done through one of the longtail boat trips booked through the tour company or directly through the national parks service.
From Mai Ngam beach, you can take a jungle walk, the trail leads you south over the mountain to the Royal Navy SARS camp, and then further south to the second National parks center at Chong Khad Beach. Do keep in mind that you have to walk back and the trail offers no lights or help points. Thus the walk is best done during the morning, taking 2-3hrs (per way), especially for families with children.