Al Stewart, as you might have noticed, writes a lot of songs about history and historical figures. Which goes to make him one of the most educational and intellectually stimulating songwriters. It is, justly, the thing he’s most known for. But he also writes about other, more contemporary, things, and that side of Stewart is just as intelligent and verbose. This song, I think, is about a sailor trapped alone in a submarine. He may the last survivor of some battle or mutiny, or he may be a ghost. He may not even be in a submarine. He could be a ghost in a sunken ship. I like to think he’s the last man standing after the rest of his crew fell victim to some deadly virus or something. However you choose to interpret those details, it’s clearly a song about being lonely and isolated in a dark, strange place. It could be a metaphor for the alienation of modern life and how the technology that keeps us alive also keeps us trapped. Or you could view it in a much broader sense as a picture of the essential loneliness of human life in general. Some of us are forever doomed to sitting in a tin can out in space, or under the sea, or behind a wall of our own creation. There is also a fear of death and the unknown, a theme that runs hand in hand with alienation and sadness. That you can interpret directly from the title; there is nothing more inherently creepy and metaphorically reminiscent of our own barely plumbed subconscious that deep sea waters. Any body of water bigger than a puddle is a mysterious realm to us, potentially fraught with horrific things from invisible but deadly bacteria to literal sea serpents and krakens. Dark water is the go-to metaphor for the endless terrors of the unknown. Because the unknown is exactly what the ocean is full of. All in all, a profoundly existential song, but it has got a nice melody, so you may not instantly catch the true meaning.