Additional information from various sources
Aircraft went down at 1722 local (i.e. sixteen minutes after sunset); aircraft out of Trenton-Robbinsville airport in New Jersey (N87); pilot and passenger wearing life vests and many police launches quickly on scene, both of which factors no doubt account for their survival; aircraft not receiving ATC services, so presumably they were flying the Hudson low-level VFR corridor.
I've flown that route myself, and great fun it is too, but I've done it in daylight, during the summertime, and always wearing a life vest. After dark, below 1,300' AMSL (the ceiling of the corridor) and with water temperatures close to freezing (hence, survival time measured in minutes) seems to me to be stacking the deck against oneself just a bit.