Gargantua (1998)

Marine biologist Jack Ellway and his son Brandon are drawn to the Polynesian island of Malau to study the effects of recent seismic activity on the area's marine life. Along with the local doctor Alyson Hart, they soon become caught up in the investigation of a series of recent drownings with unexpected results. As Jack explores the surrounding ocean for a mysterious marine creature, Brandon discovers and befriends a three-foot-long baby creature that is able to leave the ocean and walk on land. As more dangerous and giant creatures come onto the island, and the military begins to take offensive action, Jack must risk everything to save the creatures, the island and his son.