Seahound

Large beast, unaligned
Armor Class: 13 (natural armor)
Hit Points: 60
Speed: 35 ft.

STR: 17 (+3)
DEX: 15 (+2)
CON: 15 (+2)
INT: 10 (+0)
WIS: 12 (+1)
CHA: 10 (+0)

Skills: Perception +3, Stealth +4
Damage Vulnerabilities: bludgeoning, piercing, and slashing from nonmagical attacks that aren't silvered
Damage Immunities: cold
Senses: darkvision 60 ft., passive Perception 13
Languages: understands Aquan and Sylvan
Challenge: 1 (200 XP)

Keen Hearing and Smell: The Seahound has advantage on Wisdom (Perception) checks that rely on hearing or smell.
Pack Tactics: The Seahound has advantage on an attack roll against a creature if at least one of the Seahound's allies is within 5 ft. of the creature and the ally isn't incapacitated.

Actions
Bite: Melee Weapon Attack: +5 to hit, reach 5', on target. Hit (2d6 + 3) piercing damage. If the target is a creature, it must succeed on a DC 13 Strength saving throw or be knocked 10 back.
Water Charge: If the hound moves at least 10 feet straight toward a target and then hits it with a bite attack on the same turn, the target takes an extra 13 (3d8) freezing damage and must succeed on a DC 13 Strength saving throw or be knocked back 10'.
Horrifying Howl (1/Day): Each creature of the hound’s choice that is within 60 feet and is not deafened must succeed on a DC 12 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the fear on a success.