Doctor at Sea; by Richard Gordon.

It is a long time since I read this series - the Doctor series by Richard Gordon - beginning with this one, and this one stands out in memory perhaps because it was the first one, unless it was because of the doctor who was fed up at the end of the first voyage in the job he took on a ship hoping for a cushy job, much money and hardly anything to do - which was all fine and true, only the captain's wife was seasick every morning, no matter what he gave her, regular as a clockwork, and he came off feeling a failure for being unable to cure her seasickness.