Then we also had Gordon Watts of East Carolina, Tidewater, (who I
understand on a survey back in the 1970's under a contract with the
State of North Carolina found the wreck of the  "U.S.S. Monitor" which
is having more trouble than was anticipated apparently) His company
did a  marine archaeology survey of the Foundry Cove and the Hudson
River waterfront. He used some transponders that we set up on
relocated old U.S. Coastal Survey monuments on the west side of the
river so we would have translatable coordinates into the State Plane
system, so I could sync up the clients and USGS maps and coordinates
with the magnetometer surveys in the water, on the marsh and on land.
Once any anomalies were located we could report them and propose
further investigation. A side scan sonar survey was also done. The
infrared tachymeter (total station ca. 1992) worked well enough that
in calm water I was able to site in the mirror on the boat in calm
water fast enough to locate each of the mag readings. Not much was
found though in the Cold Spring, NY underwater waterfront (modified
severely also, once the location of a huge blast furnace and
production shops, some for wooden moulds for iron casting production).
I was given to understand the remains of almost all wooden boat parts
were found when they drained Foundry Cove, as confirmed by a report in
the local press.