Man-of-wars are found, sometimes in groups of 1,000 or more, floating in warm waters throughout the world's oceans. They have no independent means of propulsion and either drift on the currents or catch the wind with their pneumatophores. To avoid threats on the surface, they can deflate their air bags and briefly submerge. http://animals.nationalgeographic.com/animals/invertebrates/portuguese-man-of-war/.
I guess they got trapped in currents and debris pushed north due to early effects of Tropical Storm Andrea.
We saw lots of Man-o-War washed up along the shore of Buzzards Bay yesterday from Chapoquoit to Woods Hole. This one isn't the best one but I had to run back and get my camera and then this is the only one I could fine.