Antonio "Tottoi"

About

A young boy who, with his father and younger sister, returns to the sunny Mediterranean island of Sardinia following the death of his mother. Living with his aunt and uncle, Antonio, who is nicknamed Tottoi by his cousin, helps rebuild the old family home and enjoys swimming in the sea.

In the ancient sea caves, Tottoi discovers an adult Seal and her pup, long thought extinct on the island. He intends to keep his discovery a secret but word soon gets out and it is not long before sinister men are interested in profiting from Tottoi's discovery.

( http://www.anime-games.co.uk/VHS/anime/tottoi-secret-of-the-seal.php )