Propeller of the steamer <i>Choctaw</i>
<a href="https://en.wikipedia.org/wiki/National_Oceanic_and_Atmospheric_Administration" class="extiw" title="w:National Oceanic and Atmospheric Administration">National Oceanic and Atmospheric Administration</a>, <a href="https://en.wikipedia.org/wiki/Thunder_Bay_National_Marine_Sanctuary" class="extiw" title="w:Thunder Bay National Marine Sanctuary">Thunder Bay National Marine Sanctuary</a>
<a rel="nofollow" class="external free" href="https://web.archive.org/web/20181221121121/http://oceanexplorer.noaa.gov/explorations/17thunderbay/summaries/final/final.html">https://web.archive.org/web/20181221121121/http://oceanexplorer.noaa.gov/explorations/17thunderbay/summaries/final/final.html</a>