Help me ID an old movie.?

This movie has several collage guys going on a cruise trip and in one location some guy gives them a cette tape before dying (he was shot). When they listen to it, the recording caused them to hallucinate vividly, "It's like dope!". One even separated the signal and encoded it into a music tape and played it on the pool deck of the cruise ship they were on. They also got involved with a crooked CIA agent but they had the last laugh on him when they slipped a tape with the signal on it into the car they were riving, which he stole, and the tape ended (with him coming to) just after he drove off a cliff. I think the move dates to the 80's.