Skum

Medium Aberration (Aquatic)
Hit Dice: 2d8+2 (11 hp)
Initiative: +1
Speed: 20 ft. (4 squares), swim 40 ft.
Armor Class: 13 (+1 Dex, +2 natural), touch 11, flat-footed 12
Base Attack/Grapple: +1/+5
Attack: Bite +5 melee (2d6+4)
Full Attack: Bite +5 melee (2d6+4) and 2 claws +0 melee (1d4+2)
Space/Reach: 5 ft./5 ft.
Special Attacks: Rake 1d6+2
Special Qualities: Darkvision 60 ft., amphibious
Saves: Fort +1, Ref +1, Will +3
Abilities: Str 19, Dex 13, Con 13, Int 10, Wis 10, Cha 6
Skills: Hide +6, Listen +7, Move Silently +6, Spot +7, Swim +12; racial bonuses
Feats: Alertness
Environment: Underground
Organization: Brood (2–5) or pack (6–15)
Challenge Rating: 2
Treasure: None
Alignment: Usually lawful evil
Advancement: 3–4 HD (Medium); 5–6 HD (Large)
Level Adjustment: +3

This creature looks like an abominable crossbreed of human and fish. Its fins have grown into twisted arms and legs, and its bent back is crowned with a long, spiny frill. It has a slender, muscular tail and bulbous eyes.

Skum are misbegotten creatures created by aboleths to serve as beasts of burden and slaves. They are derived from human stock, making them even more loathsome.

A skum is about the same height and weight as a human. Skum speak Aquan.

Combat

In the water, skum are dangerous enemies who attack by biting, clawing, and raking with their rear legs. Skum serving an aboleth are sometimes trained to fight with weapons, usually two-handed melee weapons with reach (such as longspears) and simple ranged weapons such as javelins, tridents, or slings.

Rake (Ex): Attack bonus +0 melee, damage 1d6+2. A skum also gains two rake attacks when it attacks while swimming.

Skills: Skum have a +4 racial bonus on Hide, Listen, and Spot checks underwater.

A skum has a +8 racial bonus on any Swim check to perform some special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.

Source: Monster Manual (version 3.5), page 228.