There's no changing it, really--the airport is in one of the only places on the island where it can be, and prime beach space isn't going to just get abandoned because an airliner might do a belly-flop there someday.
Here's a link from the Aviation Safety Network. As you can see on the map, there's really nowhere else to put the airport. They had to build up some land on the inland salt pond to extend and modernize the runway in 1997. And note: no accidents ever reported at SXM. So, scary as it seems, the airport has a very solid safety record.
Aviation Safety Network > ASN Aviation Safety Database > Airports > Sint Maarten-Juliana Airport profile