I dont think you can get a can to that beach in St Maarten. Maybe a really long ferry ride??? Sorry, that beach is in St Thomas I believe. Are you talking about Orient Beach? The one that has a section for nudity? Ive read you can catch a cab to and from. Not sure about the price.
Taxi to Orient was 7 bucks in April( van taxi, there is a stand right at the port) great beach, sitting in a lounge chair( rent for two with an umbrella was 14$) enjoyed a Heinken( 3.00$ at bar behind us, but down the beach 50 ft and I got the next round at 2 bucks each!!!)
Magens Bay beach is nice , but too crowded( and it cost 3 bucks to get "in") and no snorkling, try Coki instead. Taxi was 7 bucks( I think , I'm a bit fuzzy on that one)