Date with a Dead Man — Brett Halliday

A strange disappearance leads Mike Shayne to investigate a death on the open sea

Mike Shayne is savoring a nightcap when his secretary calls in a panic. Lucy Hamilton doesn't scare easily and as soon as Shayne hears her voice, he knows this must be a matter of life and death. Hamilton's neighbor has vanished, and only Shayne knows Miami well enough to find him. One of only 2 survivors in a recent plane crash, Jasper Groat had been acting strange ever since his life was spared, and tonight, he walked away and didn't come back. The “lucky” survivor was carrying a deadly secret.
 
During the 9 days he spent adrift at sea, Groat filled a diary with damning details about the accident and its aftermath. There are people who might kill to get their hands on the incriminating journal -- that is, if Shayne doesn't find it first.
 
Date with a Dead Man is the 32nd book in the Mike Shayne Mysteries, but you may enjoy reading the series in any order.