Same reason Dad couldn't go in after the kid.
The boat had capsized. According to NOAA, the surface water temp. in the Sound this time of year is around 45 degrees. There's no hard and fast rule about how long you'd last in that cold, but the range is from "not very long at all" to "a few minutes". If you don't have your PFD on, all bets are out the window -- cut your survival time in half, then in half again.
I can't tell you that I'd jump in that water, unless it was my own kid. Your chances of becoming the next victim needing rescue are pretty high in that scenario.
That's the reason they didn't go in. Might be talking about a couple more fatalities, if they had gone in to try to save him.
Ok. Thanks for the response.