From all the different settings and modes you've used it's clear you were experimenting to find the right combination to get a correctly exposed picture.
Which I think is the fun part, learning how to improve.
I am no expert but do enjoy this type of photography. Can I suggest another way in which you can approach this.
Obviously use a tripod
Set the ISO to 100
Set the camera to 'Bulb' setting
Set the lens to a mid aperture (something like f/8- f/10)
Pre focus the lens to a point approx a third of the way into the scene. (On your picture the first Narrow boat would be fine)
Then hold the shutter open either by keeping your finger on the Button (but ideally with a cable /remote release) and count to 5 seconds, then release.
Keep the same settings and take another shot but hold the shutter open for 10 seconds
Then again for 15 seconds
If it,s a particularly dark scene I suggest another 2 shots at 20 and maybe 30 seconds.
Then compare the results and see which has the best lighting. You may need to adjust the time the shutter is open to maybe 8 sec's or 12 or 18.
If you do this quite often you soon learn how to read a scene, and guess more closely how long the shutter needs to be held open for.
The last several shots in my portfolio were taken using this technique.
Hope this helps and keep on experimenting.