Officials say a seal that has been spotted lately in Boston's Charles River is likely drawn to the water body for its abundance of freshwater fish.

The Boston Globe reports experts at the New England Aquarium believe that the adult harbor seal has learned it can get from Boston Harbor to the river through the locks of the Charles River Dam.

Massachusetts Department of Conservation and Recreation staff found a seal swimming in one of three locks on Monday. The locks are opened and closed for a variety of reasons such as allowing spawning fish to pass through.

Seal sightings have been reported frequently within the last 11 days, but it's unclear if it's the same seal each time.

Harbor seals can survive in fresh water for weeks.