How Neanderthals are linked to surfing?

Exostosis is a disease characterised by bone formation in ear canals. It appears as a result of hypothermia of the inner ear, that's why it usually affects surfers - people who spend hours in the water. The unofficial name of exostosis derived from this fact and the name is  "surfer's ear". 

Recently scientists examined skulls of ancient Hominidaes and concluded that Neanderthals suffered from this illness often. How come human ancestors had such a peculiar disease?

It is known that Neanderthals avoided the coldness and of course, they didn’t surf. One of the hypothesis states that our ancestors were freezing during the haunting for aquatic habitats. But it is doubtful too: all researches show that fish was the smallest part of Neanderthal's diet.  There is another curious detail: other human ancestors suffered from this illness rarely.

So maybe it might be connected to the genetic mutation? This theory has been unsuccessful too! After meticulous analysis of skulls, it was discovered that mountain inhabitants did not suffer from this malady at all: mainly, the coastal population was exposed to the exostosis.  On the one hand, the connection with water is established. On the other, it is still unclear how exactly the water affected Neanderthals.