From the Roosevelt Island Twitterverse:
WTF @ The Octagon (Roosevelt Island) https://t.co/caV996VRXl
ScottyP (@scottpiro) July 24, 2015
In August 2013 and February 2012 reported on a similar sighting.
@Rooseveltisland there was also what looked a lot like part of a submarine, on a barge. Anybody else saw it? pic.twitter.com/mU8RkKAxPF
Nicolas Robine (@notSoJunkDNA) August 26, 2013
@ibookery @Rooseveltisland yes, heading North. Here is another picture, with Presbyterian hospital in the background pic.twitter.com/DaUvPefTuK
Nicolas Robine (@notSoJunkDNA) August 26, 2013
A reader speculated the 2012 sighting was:
I think it’s the tail section of a Virginia-class submarine. Look at the diagonal fin on the bottom, then look at the back of the sub in this picture:
http://www.globalsecurity.org/…(At first I thought it was the tail of a Seawolf, but they’re not building any more of those, apparently – the Virginia’s are smaller and cheaper)