Minecraft wiki entry for Riptide, associated text: If the player collides with a mob or another player, the trident deals throwing damage, including critical damage if the player is falling. Throwing a Riptide trident consumes 1 durability‌[JE only]. Colliding with a mob to deal damage consumes 1 durability regardless of version, which means a collision on Java Edition damages the trident twice. If the Riptide trident is in the offhand, damage is dealt with the item in the main hand.