Wereseal

Wereseals were an uncommon type of lycanthropes that could shift between shapes of a humanoid, seal, and a hybrid of the two.

Description
In humanoid form, wereseals shared some slight resemblance to their animal appearance. Wereseals varied in size but an average human wereseal's animal form reached  in length and weighted double their human form's weight.

Wereseals' hybrid form, sometimes referred to as seal-men, had heads of a seal atop a human body with thick waterproof seal fur and webbed appendages.

Abilities
Wereseals had a good sense of touch, hearing, and eyesight; however, their sense of smell was poor and useless underwater. They were great swimmers and could swim as deep as. They could remain submerged for almost 30 minutes, but they were required to rest for such long dives.

Mature wereseals gained the ability to use the true sight ability three times per day, allowing them to see things hidden, invisible, and into the Ethereal plane. With time, the sight became even more potent, revealing to wereseals creatures' and objects' true forms, powers, and moral natures.

Lycanthropes, including wereseals, were carriers of lycanthropy a disease transmutable via bite.

Wereseals, and other lycanthropes were venerable to wolfsbane. Many wereseals feared it and could flee from adventurers who were armed with the plant. Wereseals could only be harmed by silver, magical weapons, or spells. Wereseals specifically were vulnerable to weapons carved out of whalebone and whale tooth, as well as amaranth.

After death, wereseals reverted to their humanoid form.

Personality
Wereseals were playful and chaotic beings. They considered tipping fisher boats over to be great fun.

When in their animal form, lycanthropes could not speak any languages, apart from communicating with other wereseals or regular seals. When underwater, they communicated by expelling air bubbles.

Combat
Like other lycanthropes, wereseals rarely wore armor. They possessed the ability to summon seals in times of need.

Society
Wereseals inhabited cold waters and stayed close to seacoasts. Females were more common than males among wereseals. Females tended to be not aggressive, while males were significantly more dangerous. Two to four females usually accompanied one bull. Male wereseals were known to form bather packs that counted up to ten individuals; however, lone were seals were a common occurrence.

Male wereseals went into heat every spring and sought female wereseals out or kidnapped and turned human women into lycanthropes.

Ecology
Wereseals consumed most any animals available but usually focused on fish and squid.

Some species of animals could detect wereseals and other lycanthropes and generally disliked all werebeasts. Such animals included horses, making them react with fear and panic when near lycanthropes or from a mere whiff of their smell. Weredolphins were natural enemies of wereseals and weresharks.

Outside the Prime Material plane, wereseals inhabited the Domains of Dread.

Appendix

 * Selkie