Hyouryuu

It's the end of 21st century. Five high-school youngsters are out camping near Tokyo. Suddenly, they are transported into a different place. It looks like a jungle. It's very hot. And it's certainly not Japan. As the heroes investigate the surroundings, they realize that they were taken to Lagoon Republic, a mysterious independent country on a tropical island that has been the home of a bizarre incident over seventy years ago. Now the young people have to find the truth behind their presence in Lagoon, and to solve the mystery of the island, while avoiding the dangers that await them.

[From Moby Games]