Fishfolk Sword

Weapon (any), uncommon
  Coastal fishfolk typically repurpose scavenged steel from less fortunate adventurers into wicked blades, adorn the hilts with coral and seashells. It is common practice to bless such a blade with water before battle; sometimes this can even attract the deep one’s blessing.
  Blessing of the Deep. As an action, you can coat this blade with water and make a quick prayer to the deep one. The water turns to flawless ice and the blade deals 1d6 additional cold damage on a hit for the next minute. Once you have used this property, you can’t do so again until the following dawn.
  Hydrodynamic. Attacking while underwater doesn’t impose disadvantage on attack rolls you make with this weapon.