<p>See the "hot load" marking? This end is far from the turning propellers. The original S-2 Trackers had an extensible Magnetic Anomaly Detector (MAD) boom. In their golden years, the S-2s had all that stuff stripped out, along with the sensor operator's stations, weapons bay, sonarbouy ejectors in the engine nacelles, tail hook, etc. The retardant tank bolts in where the weapons bay was, and a pipe that starts here runs through to it. 
</p><p>Note the leading edges of the flaps are painted red, a convention for Naval aircraft. Stuff that should be closed or hidden is painted red - edges of gear doors, top/forward part of flaps, underneath extensible slats, etc. This makes it easy for people to spot loose or unsecured stuff and tell the flight crew.
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<a rel="nofollow" class="external text" href="https://www.flickr.com/people/9998127@N06">Bill Abbott</a>
CC BY-SA 2.0
<p><a rel="nofollow" class="external text" href="https://www.flickr.com/photos/wbaiv/4310551689/">S2 Refill pipe for fire retardant reloading with engines running.</a>
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<ul><li>Uploaded by <a href="//commons.wikimedia.org/wiki/User:High_Contrast" title="User:High Contrast">High Contrast</a></li></ul>