I was actually thinking about that last night for a while, and my friends situation could have been a middle ear squeeze rather than cold water vertigo. I am reading It doesn't take much to get vertigo if the pressures in your middle ear are not equal.
This would make sense on why he couldn't come up, because a reverse squeeze would make the situation worse. I think this is why that mask is so important for my son, his middle ear will not equalize upon ascent without it.
Crazy how similar their descriptions of the symptoms were. I was skeptical at first of him, as you can imagine I thought he wouldn't want to dive again because he got into a fight with a bull shark.
Alternobaric vertigo can happen when one ear equalizes before the other. It doesn't need to get to the level of barotrauma to cause problems. It's pretty rare, I've only seen it personally a handful of times, but it can be a frightening experience, especially under water.
Differential diagnosis of vertigo can be difficult. Diving-related causes can include cold water ingress into the external ear canal or middle ear in the setting of tympanic membrane rupture (caloric vertigo); alternobaric vertigo as described above; inner ear barotrauma; contaminated breathing gas; hypercapnia (CO2 toxicity) and decompression illness. A diver who experiences vertigo that doesn't resolve quickly should seek immediate medical help.
Best regards,
DDM