Cleon
Legend
Endurance appeals, and I don't mind hold breath. However, if we use hold breath, will we need to remove the Aquatic subtype? Since it is technically a fish, that feels odd.
The Aquatic subtype means it breathes water and uses the drowning rules when out of the water. That's supported by examples such as:
Water Dependent (Ex): Sahuagin can survive out of the water for 1 hour per 2 points of Constitution (after that, refer to the drowning rules).
Thus, the breath the Icetail's holding with its Hold Breath is water, and it determines how long it can stay in the air before it needs to check against drowning.