Large anti-terrorists buoys block the entrance to a submarine drydock in San Diego harbor. Presumably, the net is to prevent viewing of the submarine; however, its efficacy is in question.
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/10393601@N08">Rennett Stowe</a> from USA
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/tomsaint/2707074939/">Submarine Drydock</a>