The spell requires a reagent, [Shiny Fish Scales], which is dropped by most aquatic mobs. There is a minor glyph available that removes the reagent cost.
Talent improvement[]
[Mental Quickness] reduces the mana cost of all instant cast spells by 6%.
Tips and tactics[]
Warlocks have a similar spell, [Unending Breath], that requires no reagent. If there is a Warlock in your group and you do not have the glyph to remove the reagent cost, allow them to buff. In addition, Warlocks can also obtain a Glyph which increases swim speed if buffed with Unending Breath, another potential benefit to letting them do it.