SELKIE
Medium-Size Shapechanger
Hit Dice: 3d8+3 (16 hp)
Initiative: +7 (Dex, Improved Initiative)
Speed: 30 ft, swim 90 ft
AC: 18 (+3 Dex, +5 natural)
Attacks: Bite +5 melee; or longsword +3 melee
Damage: Bite 1d6+1; or longsword 1d8+1
Face/Reach: 5 ft by 5 ft/5 ft
Special Attacks: Spell-like abilities
Special Qualities: Alternate form
Saves: Fort +4, Ref +6, Will +4
Abilities: Str 12, Dex 16, Con 13, Int 13, Wis 12, Cha 14
Skills: Disguise +6, Hide +7, Listen +5, Move Silently +7, Spot +5, Swim +5, Wilderness Lore +5
Feats: Improved Initiative, Weapon Finesse (bite)
Climate/Terrain: Cold aquatic
Organization: Solitary or tribe (12-30 plus 1 leader)
Challenge Rating: 2
Treasure: Standard
Alignment: Usually neutral (with good tendencies)
Advancement: By character class
Selkies are creatures that resemble seals, who have the ability to adopt humanoid form. In their true form, they look like normal seals at first glance, but they have humanoid legs and webbed hands where flippers would be. Though not a lycanthrope, the selkie is often referred to as a “sealwere”.
In humanoid form, selkies like to visit the surface world (or “otherworld”, as they call it) for brief times out of simple curiosity. At other times they have a quest, seeking information or necessary supplies. Selkies who visit the otherworld many times sometimes acquire a taste for heavy ornamentation, wearing fine clothes and jewelry. They also gain an appreciation for human customs, food, and fine wines. Such selkies blend in better with humans and often serve as diplomats.
COMBAT
Selkies usually do not carry weapons underwater, as they cannot swim rapidly while carrying anything. They bite when cornered, but prefer to swim away when opponents are too powerful. On land, selkies carry weapons that they have scavenged from shipwrecks.
Alternate Form (Ex): Once per month, a selkie can transform into the form of a humanoid, usually human, for as much as one week. This form is very attractive, and tends to garner attention from the locals. Their human eyes are always a bright, shiny emerald green or light blue. This transformation is non-magical and cannot be dispelled, but true seeing spells will reveal the selkie's true form.
Spell-like Abilities: Once per day, once per round – augury, cure light wounds, and cure disease. Once per week – weather summoning and control weather. Venerable leaders among the selkie gain these powers as they age, as selkies are not born with them. They do not use these powers for ill, lest the sea take out its vengeance on them.
SOCIETY
In a selkie tribe, females account for about 2/3 of the population. Females serve in a domestic capacity, while males hunt for fish, crustaceans, and seaweed. The sexes are equally respected within the lair and the community.
Selkies prefer colder waters, and lair in large underwater caverns and grottoes with pockets of air. They often build their lairs near sunken ships, which they explore and pillage for pearls and magical treasure. Such items are used in service of the community, and for defense of the lair.
The selkie first appeared in the Monster Manual II (1983). They also appeared in Monstrous Compendium Volume 2 (1989), and the Monstrous Manual (1993).
Edit: The "Silkie" from Dragon Magazine #41 is very similar to the well-known selkie, but they are definitely different creatures.
i was talking about new conversions i have done from the original monster manual II. 
first off are the selkie and the taer. soon to follow will be the pyrolisk, muckdweller, and carnivorous flying squirrel. 
