Red Tide (2011)

Red tide, a toxic algae bloom, infiltrates a small Florida town, leaving its economy in ruin and forcing the local fishermen and divers to do whatever they can to make a living. Alex Nikoladis returns home from prison to find that his older brother is wrapped up in a world of drugs, lies, and death. Alex's only hope for redemption from his rebellious past is to rescue his brother and return to the family trade of sponge diving--that is, without drowning in the red tide.