Also, nuke subs can (and do) leak radioactivity into the water. IIRC- and I don't have a source for this (might've been thedrive?)- Russia has radiation-detect

Also, nuke subs can (and do) leak radioactivity into the water. IIRC- and I don't have a source for this (might've been thedrive?)- Russia has radiation-detecting equipment onboard their subs that helps them in their hunt to find U.S. subs.