Can a person stay hydrated without drinking anything?

In his book, Kon Tiki, Thor Heyerdahl observed that the guy whose job it was to steer the eponymous raft across the Pacific Ocean would, despite being in the hot sun for some hours at a time, not need a water break. He proposes that this might be because the skipper was almost continuously being hit with waves.
It seems to make some sense, but over the years we’ve learned that many of his observations turned out to be only partly correct.
I nearly died of dehydration over Christmas due to a killer sore throat, was thinking that if soaking yourself works, long baths might be less expensive, more practical than going to the ER for an IV.