sea time

noun, time spent at sea in service (“sea, n.” OED)

“Through the work that I did at the locomotive company, I was able to write for a marine engineer’s fourth-class exam because of related work that I did, and they used that in lieu of sea time. Like in order for you to write for your first marine engineer’s exam, you have to have 36 months at sea in the engine room. Well I didn’t have that, but they took the time that I’d worked at the locomotive company in lieu of sea time.”