The deaths at the "Super Pond" occurred less than a month after another diver died in the same water at the Aberdeen Proving Ground, The Baltimore Sun reported Tuesday.
The two deaths occurred about 2:30 p.m. at the Unexploded Ordnance Range pond, also known as the Super Pond.
Rescue workers from the base found one of the divers dead when they arrived. The other diver was pronounced dead at a hospital.
The divers were in cardiac arrest when they surfaced at the pond, a Harford County emergency response worker said.
The divers had been tethered together while working in the pond and were using air hoses, not scuba tanks, the emergency worker said.
The identities of the divers were not released pending notification of relatives.
On Jan. 30, an engineer at the Aberdeen Test Center, George H. Lazzaro Jr., died while doing routine maintenance at the pond.
Base officials said Lazzaro's death was not related to that of the two divers.
The 1,070-foot-long Super Pond is used to conduct shock tests for ships, boats and submarines.