For thousands of years the Mediterranean Sea has shaped the course of human events. But today, its heritage of history and nature is at risk. The search is on for a killer algae that escaped from Monaco's aquarium. An unlikely candidate to combat the algae is a voracious sea slug from Cape Canaveral, Florida. Also, an ancient reed boat is constructed using the Mediterranean's last healthy patch of papyrus; hi-tech subs search for shipwrecks; and monk seals, whales and tuna are part of a detailed look at animals and mammals of the Mediterranean.