Pick up a living flow urn, empty. There are up to 8 of them at any given time in the alcove at ( -224, 37, -707 ) /waypoint -224, 37, -707. There is also another set of them at ( -224, 37, -1000 ) /waypoint -224, 37, -1000 If there are none, wait a few minutes and they will re-pop. They are LORE so you can only get them one at a time. There is a five minute wait between picking up multiple urns.
Take the filled urns and dump them into the Urn of Devotion located at ( -126, 41, -780 ) /waypoint -126.11, 41.24, -780.49 by right-clicking on the Urn of Devotion. You have to jump down to the the lower level of the structure from the entrance bridge.
Take the filled urn and dump it into the Urn of Purity located at ( -130, 40, -955 ) /waypoint -130, 40, -955 by right-clicking on the Urn of Purity. You have to jump down to the the lower level of the structure from the entrance bridge.
Return to the underwater chest and collect the reward
NOTE: A vase that pours water is a ewer. An urn is normally a decorative vase or container. The items, however, are called urns in-game except in ONE piece of the quest text, where it says ewer. We will call them urns here until such time as SOE changes it one way or the other.