River Otter

The majority of otters are fresh water dwellers. Equipped with long, slick bodies and powerful tails, river otters can be as small as 2 feet long and 2 pounds in weight to as large as 6 feet long and 100 pounds in weight. Though they are generally not aggressive towards humanoids, they can be ferocious if provoked or if they view something as prey.
Pack Hunters. Although river otters can hunt for small creatures on their own, many have been known to coordinate their attacks in pairs or larger groups. Often times, this involves cooperative fishing efforts, as otters work together to direct fish towards their pack mates. Sometimes their pack hunting can also be used to bring down larger creatures that would otherwise be beyond the capabilities of a single river otter.

River Otter CR: 0 (10 XP)

Tiny beast, unaligned

Armor Class: 12

Hit Points: 1 (1D4 -1)

Speed: 20 ft , swim: 40 ft

STR

3 -4

DEX

15 +2

CON

8 -1

INT

6 -2

WIS

12 +1

CHA

6 -2

Skills: Perception +3

Senses: Darkvision 30 ft., passive Perception 13

Challenge Rating: 0 (10 XP)

Keen Sight. The otter has advantage on Wisdom (Perception) checks that rely on sight.
Hold Breath. The otter can hold its breath for 10 minutes.
Pack Tactics. The otter has advantage on attack rolls against a creature if at least one of the otter's allies is within 5 feet of the creature and the ally isn't incapacitated.

Actions

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 1 piercing damage.