R-8 fitted out at Boston, Massachusetts, during the fall of 1919, proceeded to New London, Connecticut on 5 December, joined other boats of Submarine Division 9 (SubDiv 9), and continued south for winter exercises in the Gulf of Mexico.

Given hull classification symbol "SS-85" in July, she departed Newport, Rhode Island on 13 September and two days later arrived at Norfolk for overhaul prior to transfer to the Pacific Fleet.

In late October 1925, she collided with the minesweeper USS Widgeon (AM-22), suffering the loss of her periscopes, the destruction of her bridge, and damage to her radio antenna supports.

Ordered back to the East Coast for inactivation in 1930, R-8 departed Pearl Harbor on 12 December, transited the Panama Canal in mid-January 1931, and arrived at Philadelphia, Pennsylvania, on 9 February 1931.

CORMORANT’s log provided the sinking location as being far offshore from the VA-NC border in ~4,300’ of water: nearly 70 miles south of where it was previously thought to be.