Rich, Gate City is a fun dive but lies in the surf line at Moriches. I’ve d one the dive twice, both times off a boat on a flat day. On the right day it’s a great dive. You can see the wreck from above as it sits in 12 feet of water. GPS 40.7629N 72.7386W. Good luck, have fun.
On another note, I saw you are looking to dive the bridge. LIDA is hosting a Marine Biology Dive Night at the bridge. Friday, August 17th beginning at 6:30PM, Ponquogue Bridge Marine Park, Hampton Bays (High tide is at 8:40PM)
"Join LIDA for this special dive event as we collect marine organisms for identification and discussion. Marine biologist Marianne McNamara and fish extraordinaire Steve Abrams and other local experts will be on hand to describe and identify the various marine life found within Long Island waters. Numerous local outreach organizations will be represented, including the Riverhead Foundation for Marine Research and Preservation, New York Sea Grant and Long Island Sound Study."