First World War submarine activity in the Mediterranean

Was there U-boat activity in the Mediterranean during the First World War?

Yes; there was extensive activity, with Austro-Hungarian submarines especially important and dangerous.

The Mediterranean saw substantial submarine activity during the First World War. German U-boats tried to enter the theatre, while Austro-Hungarian boats formed the central local threat. Those submarines were especially dangerous despite the campaign's lower profile in Atlantic-centered accounts. The exchange points viewers toward the Adriatic as a distinct submarine operating system rather than a minor extension of the Atlantic war.