Liquid Voice

Introduced in Generation VII, Liquid Voice converts all sound-based moves used by this Pokemon into Water-type moves. This includes Hyper Voice, Uproar, Round, Sparkling Aria, and any other move carrying the sound flag. The type conversion occurs before damage calculation, meaning the transformed moves follow Water-type effectiveness rules and receive STAB from Water-type users.

The conversion changes only the move's type -- base power, accuracy, secondary effects, and all other properties remain identical. This makes Hyper Voice particularly valuable as it becomes a 90 base power, 100% accurate Water-type special attack with no drawbacks, superior to Surf in that it does not hit allies in Double Battles.

Found exclusively on the Primarina evolutionary line (3 Pokemon), Liquid Voice defines their offensive toolkit by turning their naturally learned sound moves into reliable Water-type coverage.