When I was bringing my boat up from Delaware Bay several years ago, I had a similar experience. Never hit 12 knots, but we were over 10and reached 11 knots for a good stretch.On our trip from the Chesapeake to Mystic and Block Island we hit the East River and Hell gate both ways. We left going to the LI Sound from Atlantic Highlands as the tide was turning in Lower NY Bay. We hit the Battery one hour into the flood went up the Est River at 9+ knots and made 12.1 knots through Hell Gate and made Northport Harbor (a great place) by 5 PM
The way back was even more astounding. We left Port Jefferson ( Mount Misery Cove) at 6AM hot the Throgs Neck at the beginning off ebb tide. Rocketed through Hell gate at 12.4 knots (I have a picture of the SOG on our C80 chartplotter) made the Verazano by 3 on the outgoing tide and kept going to Manesquan.
The trip at 12 knots can be somewhat scarey but need at the same time. Kind of like hitting the icy bridge going 65 mph and not wanting to even touch the steering to hard or the brakes.