quackers
... that Soviet submarines patrolling in the North Atlantic in the 1970s reported mysterious frog-like sounds, dubbed "quackers", which have been classified as Unidentified Submerged Objects?
...  that <a href="./Soviet_Navy" id="mwAzw" rel="mw:WikiLink" title="Soviet Navy">Soviet submarines</a> patrolling in the <a class="mw-redirect" href="./North_Atlantic" id="mwAz0" rel="mw:WikiLink" title="North Atlantic">North Atlantic</a> in the 1970s reported mysterious frog-like sounds, dubbed "<b id="mwAz4"><a class="new" data-mw-i18n='{"title":{"lang":"x-page","key":"red-link-title","params":["Quacker (sound)"]}}' href="./Quacker_(sound)?action=edit&amp;redlink=1" id="mwAz8" rel="mw:WikiLink" title="Quacker (sound)" typeof="mw:LocalizedAttrs">quackers</a></b>", which have been classified as <a class="mw-redirect" href="./Unidentified_Submerged_Object" id="mwA0A" rel="mw:WikiLink" title="Unidentified Submerged Object">Unidentified Submerged Objects</a>?