Did you try searching the FCC database? It is but one step available to you. I got the following under a geosearch for active marine coastal licenses in Cape May County, not including mobile areas of operation. I'm not the least bit familiar with Cape May or any marina operations so you may be better off doing a new search yourself (possibly point/radius to tighten results).
KFL349 - ATLANTIC CAPES FISHERIES INC
WQPI615 - Cape Harbor Enterprises Inc
WQA330 - CARLSON, CARL R
WHX926 - F/V LAURA ANN INC
WQNF300 - Guardian Marine Inc. DBA Sea Tow Cape May
WRV534 - H & L AXELSSON INC
KEB620 - RYAN, JOHN F
WQQY388 - TowBoat Towing and Salvage
WHF904 - UTSCHS MARINA
WHX755 - VONA, JOHN W
KPB673 - WALLACE, JAMES J
Up my way I have seen marinas license the standard calling/ distress channels plus one or two others which I have guessed may be their operations. From the above list I have omitted state and county licenses, as up by me those seem to just be related to bridges. If the county operates a marina, you may want to comb through those.