Maneuvering a regular (stern) driven boat without a bow screw at low speeds is super hard. There is this 10 year old kid at a marina near where I live that handles all of the rental boats, I've seen them do this in absolutely impossible situations with a grace and skill that really blows my mind, it's like the boat is on rails and does exactly what they want it to do. Even the box shaped 'party boats', and those are really next to impossible to move around in predictable ways.
A testament to the plasticity of the human mind. Like getting (and losing) "sea legs". You walk your whole life on solid land; now you don't for a few days and your freaky brain figures it out. You're a kid and you don't know anything about boats, but you take the job parking the rentals. By the end of the summer, they move to your whim.
But steerage at slow speed is a tricky subject. I had a trawler I was terrified of at slow speed, because it was absolutely massive, and the rudder did nothing at low speed. Plus the transmission was iffy so putting it in reverse would take from 5-50 seconds. Plus being single screw her rear-end would pull to port in reverse. Never again! (A sail-boat with a big keel and big rudder, and much less beam and mass? No problem!)
Boats are tough. I have to bring my sailboat under two draw bridges each winter. It is always a little too exciting, especially if you are unlucky enough to get stuck between the bridges which are really close together!
Here in NL we have a type of mast that can be dropped under sail and re-set right after crossing under a bridge. This is a pretty exciting operation best practiced a large number of times without the presence of a bridge before you try it for real. Failures tend to be fairly spectacular.
Here a demo on a very small boat, I've seen this done with a big Tjalk and that was most impressive (but I can't find any video of that):
With a big ship it will look like an accident is about to happen until the last moment when the sail drops, the mast gets dropped backwards and they are barely out from under the bridge on the far side or the whole operation happens in reverse resulting in very little lost speed.
My uncle developed something similar for his boat but only the top. The idea was to have a 15-ish meter high mast fit under the Hollandse Brug (12.8 meter high bridge). He put a hinge in the mast and added a lot of stays to allow this to happen.
He is a maritime engineer, so he had it all calculated out to ensure it would hold up in rough weather. And knowing how racy he sails, I am pretty sure its been put to the test.
That sounds super cool :) Interesting that he special cased it for that one bridge, and good that the water level there is reasonably stable, but that would definitely require some checking before making a run at a later date because the waterschappen are known to occasionally change their policy and suddenly you'll find that your 'known depth' is off by a meter either way. Lower wouldn't be much of a problem I guess but higher very well could be.
Yes, keel-stepped mast. I used to have a boat where I could remove the mast myself - but having a rig (that you wouldn't bring sailing with you) made it easier and less dangerous to the boat. I never did take the mast down on the water.
Most larger boats in the US do not have masts you can remove without some equipment. This is because the mast is 50-60' and really heavy. Even if it is deck-stepped, you're not going to be able to do that on the water easily.
This reminds me of something I had completely forgotten: many years ago, we spent a week cruising an English canal in a narrowboat, which have the basic setup of a fixed-in-azimuth propeller and a rudder. One morning, a guy went by backing up a sixty-footer at about 5 knots for about a quarter-mile, until he could swing the stern into a junction to turn it around. It took me a while to get my jaw up off the deck.
