At 5:40, while Nedge is turning on the sonar, some of the buttons she presses are from old electric organ consoles.
At 40:40 (approximately), in the flames, the ship that Seafield and Ashcroft sail with their father in, can be seen. Additionally, the ship is named Milwaukee Clipper.
At 41 minutes, faces can be seen in the flickering fire shot.
The waters surrounding coastal Lake Michigan are extremely cold during the spring months in many North American regions, such as Wisconsin.
At 46 minutes, Seafield is approaching the Lake X-press boat with his hat on. Yet when he enters the boat, his hat is missing. Later scenes show him with his hat again.