The waters around Nantucket are home to seals, sharks, and whales as well as other marine life. These species are federally protected under the Marine Mammal Protection Act and it is illegal to harass, harm or disturb their natural behaviors.
At Sconset beach, we commonly see gray seals and harbor seals but in winter or spring you may see harp and hooded seals. Sharks may be seen occasionally and can be identified by a dorsal fin that cuts straight through the water, unlike sunfish whose dorsal fin bobs in and out of the water.
People should avoid swimming between dusk and dawn, swim in groups, and not go too far from shore to avoid marine mammals.
More information about seals and sharks is provided below.
PLEASE REPORT injured, entangled, and deceased marine animals to the MMAN HOTLINE:
The Marine Mammal Alliance Nantucket (MMAN), www.nantucketmarinemammals.org, is the authorized marine mammal stranding response organization for Nantucket, Tuckernuck, and the Muskeget Islands.
Seals may bite if provoked and may carry diseases that can be transferred to people and pets, so getting too close can be dangerous.
Marine Mammal Alliance Nantucket offers workshops for children age 5-11 throughout the summer on the Sconset Beach to teach them about seals.
Between July and September, sandbar sharks, dusky sharks and tiger sharks gather in the waters around Nantucket and their natural prey are seals. At area beaches, lifeguards will assess whether the size and behavior of a shark requires people to remain on land. Swimming will be prohibited for up to two hours and a double red flag will be displayed if shark activity is detected.
The New England Aquarium’s Anderson Cabot Center for Ocean Life has a shark research team that tags sharks in our waters. Between 2020 and 2023, some 100 sandbar sharks between four to six-and-half feet in length have been tagged and provide valuable information to scientists through acoustic transmitter tags and identification tags. There are 14 receivers placed around the island -- buoys are yellow on the South Shore and white on the North Shore.