Pembrokeshire benefits from a mild maritime climate, brought by the gulf stream all the way from the West Indies. These same waters bring, during the summer, a concentration of plankton, fish and squid to the waters of Pembrokeshire. Such a gourmet banquet naturally attracts a few more exotic diners.
Certainly the largest creature to visit the waters of Pembrokeshire is the basking shark. This fish can grow to be as large and heavy as a double decker bus, but lives entirely on plankton, microscopic plants and animals. In summer it can be seen from the coast moving slowly through the water, either singly or in groups. Much about the life of this creature is unknown, but populations of basking shark do seem to move up the Irish Sea towards the Isle of Man.
Strangest amongst the ocean visitors is the sunfish. This fish looks almost like an enormous dinner plate, being round and flat. It swims upright with huge fins on top and underneath to steer with, or can be seen on its side at the surface, seemingly being warmed by the sun. Sunfish are regular visitors to Pembrokeshire during the summer, and can be seen from the coast or offshore islands.