If so maybe you can ask to Turkish Maritime Agency (Whatever its called in English).
http://www.tdi.com.tr/
There is an email address over there to ask: bilgi@tdi.gov.tr
Altough I believe that it is very hard to find, you lose nothing by trying . I can try to help to translate your letter, question to turkish if you need.

Was he in military? If so probably you can only find it from the Turkish Navy Military records/archive which probably not easy to find...

Try go into every bay in the Datca. As you said Knidos and center is the main attractive places for Datca peninsula but for example I recommedent you to go into Bordubet Bay and stay in Amazon Camping if you will have time. You should definetly stay at Inbuku Bay/Camping as well . You can find some photographs and places in Datca peninsula at:
http://e-turkey.net/v/mugla_datca/http://e-turkey.net/v/mugla_datca/
I am the photographer for the album and you can ask details to me if you need. My suggestion is if you want to visit no touristic places in Datca peninsula cover all the roads in Peninsula. For me it was worth to do that .

Baris

"onumuzdeki ayin 7 sinde dogum gunum var yanim daolmani istiyurum."
"I have birthday in 7th of next month and I want to be with you that day."

e-Turkey.net Turkey Guide with photographs.
www.e-Turkey.net
Provides content on historical places, cities, natural treasures of Turkey.
Actually I am the founder of this site and trying to enrich it. It is open to your contribution.
Also we should add www.turkishclass.com/pictureGalleries.php