Water rune:

A Water rune is a river rune in Dota 2 that restores health and mana when picked up. It is an early-game laning resource, usually contested by mid heroes because it can refill resources without using consumables and can help a hero stay in lane or recover after trading damage. Water runes matter because they reward rune control and create small but important timing fights around the river. For example, a mid hero that has spent mana on spells can move to the river to secure a Water rune, immediately recover enough resources to keep pressuring the lane or avoid returning to base.

Related: Bounty rune, Power rune, Rune, Bottle