Complex sentence: Probably the most useful role of the Pukaki and its sister was to escort with police launches and HMNZS Waikato the USN SSN's Haddo and Pintado into Auckland Harbour in 1978 and 1979 and deleted in 1991, being sold as a private launch.
Split into simpler sentences: Probably the most useful role of the Pukaki and its sister was to escort with police launches and HMNZS Waikato, the USN SSN's Haddo and Pintado into Auckland Harbour in 1978 and 1979. HMNZS Pukaki was deleted in 1991, being sold as a private launch.