Pirates

A young boy and his family were shipwrecked and washed up on a mysterious island. After awhile a group of pirates found the island and came ashore. They found the young boy starving and clutching a weird looking device. They found him alone. The pirates took the boy aboard and treated him as one of their own, until they were all killed that is. Now the young boy is left with a few other pirate teens alone trying to figure out how the hell they're suppose to survive on the Seven Seas.

In a universe exactly the same as ours except for one small detailed, most technological advancements stopped in the 13th century. Now the year is 1975 and things are about to get a jumpstart with a little help from a mysterious shimmering rock.