There are two types of Seal normally found on the UK coastline - the Harbour (or Common) Seal and the Grey Seal. Lindisfarne is known for its Grey Seals, which have longer snouts and wider nostrils than the harbour seal (not that it's easy to see the difference in these photos). At low tide they haul themselves out onto the sandy beach, to the south of the harbour. They can also be seen swimming in the sea all around the island.

Although a bit distant, the path up to the castle gives good elevated views of the seals on the beach in the bay opposite. You can get even better views when they are on the rocks below the castle.