Multiattack. The merrow makes two attacks: one with its bite and one with its claws or harpoon.
Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) piercing damage.
Claws. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 9 (2d4 + 4) slashing damage.
Harpoon. Melee or Ranged Weapon Attack: +6 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 11 (2d6 + 4) piercing damage. If the target is a Huge or smaller creature, it must succeed on a Strength contest against the merrow or be pulled up to 20 feet toward the merrow.
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.