Divers were dispatched to Playa Monserrate, near the town of Luquillo on the island's Atlantic coast, after a fisherman reported finding what he thought were human remains, Rivera said.
The artifacts turned up in six different spots across the sea floor, said Laura del Olmo, director of archaeology at the Institute of Puerto Rican Culture, which sent a team of experts to the site.
So far, divers have recovered more than three dozen pieces, including a small silver cross, bottles, and fragments of wood and chain, which will be analyzed by the institute's experts, del Olmo said.
According to archeologists, the pieces appear to be from the 17th or 18th century but further analysis is required before their exact age can be confirmed, she said.
Divers planned to continue exploring the area for more artifacts, Sgt. Rivera said.