Small elemental humanoid (aquatic, water)
Elemental Companion

HP 1; a missed attack never damages the companionDefenses your defenses, not including any temporary bonuses or penalties
Speed land 6 , swim 6

Passive Benefit: Aquatic

You can breathe underwater. In aquatic combat, you gain a +2 bonus to attack rolls against creatures that do not have the aquatic trait.

Active Benefit: Aquatic

The nereid can breathe underwater.

Active Benefit: Free Action (healing) Encounter

Trigger: An ally adjacent to the nereid spends a healing surge.

Effect: The triggering ally regains 3 additional hit points (6 at 11th level and 9 at 21st level).

Published in Heroes of the Elemental Chaos, page(s) 149.