Waterborne Arsenal

You create up to ten simple or martial melee weapons from available sources of water within range that last for the duration. These magical weapons have the same resilience and properties as their mundane counterparts. In addition, when a creature wielding one of these weapons makes an attack while underwater, it has advantage on the attack.

If a creature wielding one of these weapons attacks a creature that is susceptible to water, such as a fire elemental, the weapon deals extra cold damage to the target equal to its damage die (or dice).