Seagrasses provide critical ecosystem functions and services but are exposed to intense human activity in estuaries worldwide. Jetties are common boating infrastructure that have proliferated in many urbanized estuaries – causing significant reduction in access to light for seagrass, and the subsequent loss of seagrass. Identifying the features that influence the loss of seagrass will allow the design of these structures to be sustainably optimized. Previous studies have examined jetty design features on small numbers of jetties (< 6) – including features such as width, height, orientation and construction type. Here, we report on a rapid assessment approach (p/a) to inspect 328 jetties in the Port Hacking estuary (out of 923) to sample a wide range of each of these variables to determine their influence on the persistence of seagrass. Half of the mesh jetties retained seagrass (n = 11), while only 25% of the timber (plank) jetties had seagrass (n = 198) and only one pontoon had seagrass (n = 172). Jetty width and gap size were important for retaining seagrass, but height was not. These results will be used to develop foreshore development guidelines for jetties as part of the NSW Marine Estate Management Strategy.