Pack Tactics. The shark has advantage on an attack roll against a creature if at least one of the shark's allies is . within 5 feet of the creature and the ally isn't incapacitated.
Water Breathing. The shark can breathe only underwater.
Actions
Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d8 + 2) piercing damage. Smaller than giant sharks and hunter sharks, reef sharks inhabit shallow waters and coral reefs, gathering in small packs to hunt. A full-grown specimen measures 6 to 10 feet long.
RollQuest ships the D&D 2014 SRD as a content pack, on a 5e character sheet that does the maths - roll from the sheet and let the numbers work themselves out. Free to start.