Thresher (SSN-593) (sank, 129 killed) USS Scorpion (SSN-589) (sank, 99 killed) Both sank for reasons unrelated to their reactor plants and still lie on the Atlantic sea floor. [ edit ] Russian or Soviet Komsomolets K-278 (sank, 42 killed) Kursk K-141 (sank recently, 118 killed) K-8 ( loss of coolant )