Weapon

Uncommon

This vicious-looking trident is lashed together with nets, leather straps, and bloodied shark bones. When you throw this weapon underwater, it magically swims back to your hand immediately after the attack. 
  Animate Shark. While holding this weapon underwater, you can prick an exposed bit of your flesh with it using an action. When you do, the weapon springs to life and becomes animated. Use the statistics of a reef shark for the animated trident, which takes its turn immediately after yours; it's considered to be undead, instead of a beast. For the duration, the trident is friendly to only you, and it obeys your mental commands to the best of its ability (no action required by you). On its turns, the shark can take only the Attack or Dodge action. When it takes the Attack action, it makes two bite attacks, instead of one. The trident remains animated for 1 minute, and it regains all lost hit points when this effect ends. The trident reverts to its inanimate form early if it is targeted by a dispel magic spell or similar effect. Once this property has been used, it can't be used again until the next dawn. If the animated trident is reduced to 0 hit points, roll a d20. On a 20, it drops to 1 hit point instead. On any other result, the trident becomes inanimate and loses the Animate Shark property.