The federal government is poised to open up nearly all of the waters along the shores of the United States to offshore drilling, including areas that would impact the Chesapeake Bay.

Memories of oil spills such as the Gulf Coast’s Deepwater Horizon disaster in 2010 have coastal communities concerned about the potential impacts of such accidents to fisheries, tourism and military installations along the Virginia shoreline.

But the more immediate threat, according to representatives of the nonprofit environmental group Oceana, is the danger of seismic airgun blasting used to explore the ocean floor to determine where the oil deposits lie and whether it would be worth it to build oil drilling rigs.

Such blasting is a danger to fish, shellfish and marine mammals, said Loryn Baughman, communications associate in Oceana’s D.C. office, and Terra Pascarosa, Oceana’s Virginia organizer of environmental campaigns, who sat down for an interview last week in Gloucester. Nevert...