Enid Blyton - The Ship of Adventure
[ABRIDGED AUDIOBOOK like a radioshow]
            + full text

The sixth adventure for the Trents and Mannerings begins on board the Viking Star, a cruise ship that sets sail from Southampton and heads for the Greek islands. On the way, the children come across an old ship in a bottle which contains a Greek treasure map, and they set out to hunt down the treasure on the remote island of Thamis.