Grand Funk guitarist Mark Farner wrote this and sang lead. Literally, the song is about the captain of a ship who is sick and fears he is going to lose his vessel. The song has much more metaphoric significance, however. Farner explained to Nightwatcher's House of Rock
: "I had gone to bed and prayed. Our mother had taught us kids to pray the 'Now I lay me down to sleep,' so I finished that part of the prayer, and put a P.S. at the end of it, and I asked the Creator to give me a song which would reach and touch the hearts of people that he wanted to touch. With love, because I just felt the love. I just felt for my good friends, my high school buddies who had died in Vietnam. I saw their parents, and I saw their families, and I think that's what inspired it.
It came in the middle of night to me as words, and I didn't even realize it was a song, because I write words all the time. In fact, my wife has a file that she has where she's picked up napkins and notes here and there that have all these words that come out. At least we have a place to start putting them together, like a puzzle. But I grabbed those words in the morning, because I was playing my guitar in the kitchen of the farm. I was sipping on my coffee, had my feet kicked up in the chair, and I had my flattop guitar. As I was strumming the intro chords to 'I'm Your Captain,' I went, 'Hey man, maybe this is a song.' So I went and got the words, and started constructing the song out of it. I took it to rehearsal that day and the guys said, 'Man, this song's a hit.' And, lo and behold they were right."