جون هولاند
SM "U-6 or U-VI" was a "U-5"-class submarine or U-boat built for and operated by the Austro-Hungarian Navy ( or ) before and during the First World War. The submarine was built as part of a plan to evaluate foreign submarine designs, and was the second of three boats of the class built by Whitehead &amp; Co. of Fiume after a design by Irishman John Philip Holland.