You can spend 2 ki points as an action to create a whip of water that shoves and pulls a creature to unbalance it. A creature that you can see that is within 30 feet of you must make a Dexterity saving throw. On a failed save, the creature takes 3d10 bludgeoning damage, plus an extra 1d10 bludgeoning damage for each additional ki point you spend, and you can either knock it prone or pull it up to 25 feet closer to you. On a successful save, the creature takes half as much damage, and you don’t pull it or knock it prone.
From a PHB errata:
Water Whip (p. 81). “A bonus action” has been changed to “an action.”
Hello dndbeyond, in the players hand book (page 81) the water whip is a bonus action, while here it is an action.
https://www.dndbeyond.com/profile/cyberghost10/characters/33301608 sample character here.
Taken directly from the Monk source page:
From a PHB errata:
Oh my apologize then, i was not aware of the update.