Mystery on Monster Island (1981)

"On an island forgotten by time, perilous adventure awaits!"

A young European boy living in San Francisco is reluctant to marry his long-term girlfriend because he wants to travel around the world first. His wealthy uncle agrees to send him on a global expedition aboard his ship, but en route the boy and his travelling companion are shipwrecked on a remote island, populated by countless prehistoric creatures as well as gold-hunting bandits.