Best friends Ben, Justin, and Edie are surprised and excited to wind up on the same tropical cruise together. Their parents? Not so much. Ben's father Hank used to be good buddies with Justin's father Frank--but the two men have drifted apart over the years. Unbeknownst to Hank, Frank had been dating Janet at the time, and she ended up dumping Frank just before he met Hank. After graduating, they went their separate ways, and the three never figured on seeing each other again.... Until Janet's daughter Edie meets Ben at college and the two begin dating. Now all six of them are on the same cruise, and things could not get any more awkward.
To make matters worse, a freak storm blows the cruise ship through the Bermuda Triangle and the six travelers escape by lifeboat into the Amazon River--where they discover a shocking secret: Mermaids from another dimension, able to shed their scales and walk on land as the freakishly-tall Amazons of legend, have been living in the jungle for several decades. A cataclysm has tangled the two dimensions in a never-ending time loop dating back to the end of World War II--and what is more, the Amazons are being hunted down by Japanese soldiers also trapped in the time warp. Can the six adults set aside their differences and work together to escape before the Japanese soldiers kill them along with the Amazons, or will they need to figure out how to separate the two dimensions before the primitive Amazons decide to sacrifice them all?