Propane itself is odorless, but the propane sold commercially normally has a chemical added to it so it has a distinct smell. That said I don't know if the smell would awaken you from you sleep.
It does tend to pool at low points, displacing the air under it. In that situation the result is usually a flash fire more than an explosion, but some mixing with air is all it takes to turn that situation into an explosion.
It looks like there was only one way out of the sleeping quarters. I can’t imagine why the Coast Guard would approve that.