No need to do any shore excursions - all it needs is a bit of research. If you use a browser and type in the words 'message and cruise and europe' (no need to put in the 'and') - of the results returned you need approx 3rd link down that begins with the word Europe and has the word 'boards' in the title. You can then search by town/island once you have signed up. You can also search on this site for answers too. This is also an excellent site re Venice - http://europeforvisitors.com/venice/articles/local-transportation-index.htm
We have have done 3Med cruises and generally made our own arrangements for shore visits. this usually saves us up to 50% on the expensivecruise ship tours. try to team up with another couple and you will find that local taxi tours are really good value. When you visit venice take copy of the eye witness guide, there are lots of sights to see in venice and you will not have have much time if you dont pre plan.Drubrovnik is only a a short bus journey from the cruise terminal and then the old city is totally on foot. this was our best port of call on our Aidriatic cruise this October. Hope this helps KEITH.
Thank you both for answering my question, I am really looking forward to our cruise, we have done most of the western med so going to the eastern med is new to us. Thank you again. Sally.