My interpretation of "There were just us five aboard her when she finally was aswash," is that the rest of the crew had already abandoned ship, implying a larger crew than five or six. I have always envisioned her as a small to mid-sized cargo carrier. And she wasn't necessarily working the coastal fishing ground to sink in only 60 feet of water; the story also implies that she hit the rock because she wasn't where she was supposed to be, since the officers were drunk and not paying attention.