The Merrow has a Harpoon weapon attack option with the following stats:
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.
I can only assume its Str base +4 and +2 prof to get the +6 attack bonus.
Can a player take and use the Harpoon in the same way that the merrow use it?
Is this kind of harpoon listed as a weapon/equipment anywhere else?