> in my experience with a 40ft sailboat with a single propeller you have absolutely no rudder authority while reversing.
In general it depends on the rudders and the boat.
Longer keeled boats don't respond well in reverse at all but more modern boats (like mine, 1990) will do better but will still need some way to have steerage. I can certainly manouver around the marina in reverse, it's just harder than forwards and I need to be going a bit faster to get the control.
Going backwards in the marina I often steer on the engine rather than the rudder (though I keep the rudder aligned with the engine of course). Obviously that's in a tiny sailing boat with an external engine, but I thought large ships also often have a steerable front propeller to assist with steering and mooring. Although maybe these very large ships use tugboats for that.
My boat has an inboard diesel so no ability to direct the prop. It does have a bow thruster, but it's only really used at slow speed, usually right at the point of docking and undocking in tight spaces, once you get the boat moving in forward or reverse you don't need it.
I have no idea about container ship sized boats, though I'd imagine a bow thruster of steerable prop might not be practical at that scale.
All I really know about long keels is from what people have said. They tend to track well and don't tend to make as much leeway, but perhaps at the expense of speed due to the wetted area, and they are hard to steer backwards. Not being particularly manouverable forwards isn't really an issue if you're spending several hours going mostly in a straight line.
Modern flat boats (like the 2017 Dufour I learned on) are highly manouverable at slow speed, we practiced spinning the boat on the spot by using prop wash over the rudder forwards then ticking over in reverse. Could turn the boat in not much more space than the boat length, but may not track as well, may slam more, and make more leeway.
In general it depends on the rudders and the boat.
Longer keeled boats don't respond well in reverse at all but more modern boats (like mine, 1990) will do better but will still need some way to have steerage. I can certainly manouver around the marina in reverse, it's just harder than forwards and I need to be going a bit faster to get the control.