One knows of four families of mammals in the sea, dolphins (including porpoises), hippocampi, sea pigs, and seals (including walrusses).
Dolphins are fairly fishlike, but have smooth skin rather than scales, high foreheads and distinctive muzzles.
Dolphins are held to be very clever animals, often compared favourably with cats. Some men cooperate with dolphins in fishing or whaling. Dolphins may rescue victims of shipwrecks, even carrying them back to civilization.
Hippocampi resemble their terrestial counterparts from the chest forward, with fully equine heads, extremely long, shaggy manes, and a pair of hooved feet. Their bodies are twice as long as those of horses, though, with serpentine body tapering to a pair of tail flukes. Hippocampi swim with powerful tail strokes, and the ignorant sometimes mistake hippocampi for sea serpents at a distance. Hippocampoi are It is a common misconception among landlubbers that hippocampi hindquarters are covered in scales, and sailors sometimes sell a whalefish's scales as those of a hippocampus.
Hippocampi are known for their great ferocity. They roam in herds led by stallions, who fight each other for dominance, and use powerful kicks to ward off predators. Hippocampi stallions fighting are an awe-inspiring sight and a favoured motif for artists.
Hippocampi come onto beaches to give birth, and this is the favoured time for hunting them. Hippocampi meat is palatable to humans, but no more, and their hides make good leather. However, the most coveted resource gained from hippocampi is their manes, which make the strongest thread and bowstrings known to man.
Sea pigs are found mostly in temperate and tropical waters, though some species seem to thrive in colder climes. They live in shallow waters, and are rarely found in open seas. Sea pigs are herbivores, feeding on sea grasses and similar plants. Found singly or in flocks, sea pigs are a large family with a variety of species. Those living in warm waters are hairless, while those closer to the Boreal Ocean have thick, bristly pelts. Sea pigs are hunted mainly for their flesh, but also for their hides, and the ivory of the tusks of the larger sea pigs.
Seals favour northern waters, but may roam further south. They are found mainly in the Boreal Ocean and the northern part of the Ocean of Lost Souls. Seals are carnivores, living on fish and crustaceans.
Seals are gregarious animals, and may be found sunning themselves on beaches. They are hunted for meat and pelts.
The larger cousins of seals, the immense walrusses, are only found far north. They are dreadful, tusked creatures, and the ivory of their tusks is quite valuable, deeemd superior to elephantine and draconic ivory for craftmanship.