Death Beyond the Limit by B.M. Allsopp

Publisher's Synopsis

Can a landlubber detective combat evil on the high seas?

Inspector Joe Horseman stares into the eyes of a severed head. Fished out of a shark’s gut, the unknown victim is soon dubbed Jona by the media. Did the tiger shark kill Jona or was he already dead when it clamped its teeth around his neck? Horseman must battle ruthless criminals, bureaucracy and even the law itself to dredge up the answers.
But cracking the case may not be enough. Can Horseman stop this crime sinking without trace in the lawless ocean?