Into the blue 2: the reef (2009)

When they're hired to recover the lost treasure of Columbus, married scuba divers Sebastian and Dani think they've hit the jackpot. But as they get closer to the fortune, the couple begins to suspect their employers have their own agenda. Hitting upon the real plan, the two come to the chilling realization that they may be expendable and that there's much more than riches at stake.