Crackdown by Bernard Cornwell

British ex-marine Nick Breakspear, who skippers charter boats out of the Bahamas, dreams of refurbishing a classic boat and sailing off with beautiful Ellen, ship cook and practicing celibate. On the verge of realizing his fantasy, he agrees to take the cokehead son and daughter of a U.S. senator on a cruise to kick their habits. The son forces a rendezvous at sea with vicious traficantes who sink the boat, kill a crew member and almost kill Nick and Ellen. Back on land Nick is persuaded by the senator, a presidential contender, to join a three-man raid against the heavily guarded island stronghold of the drug lords.