Water Barrier was a level-2 cantrip that constructed a defensive force field made from rearranged water elements.
Angor had been studying this skill, which was usually considered as one of the worst among all defensive cantrips. Putting its combat value aside, this cantrip had a special trait that made it very useful for resisting high underwater pressure.
During the second phase of the purification garden challenge when people were thrown into the Sea of Purification, most of them could move around in the water because of this cantrip.
By that time, Angor was instead using the built-in Purification Field on his hat. Fortunately, his hat wasn't broken by any incident or he'd immediately get squashed by the deadly strength of nature.
After getting out of the garden challenge, he had been using some of his free time to read about the Water Barrier.