Did you know:
Whales don’t have to strain to hold their breath, they have no drowning-reflex and don’t breath automatically, they can only breath consciously. So while land mammals usually will start gasping for air when still underwater for too long. Whales will not.
This means whales don’t drown (because drowning means inhaling water), they rather asphyxiate underwater if they can not reach the surface.
I believe it’s the most common cause of death for old whales (for all whales it’s sadly collisions with ships). They become too weak to swim to the surface and then just sink into the deep… horrible way to go.