I got a call last year to look at a 35 foot twin engine I/O boat. The owner had run aground at night, traveling over 100 feet on shore and sheared off both out drives. I ended up waking away from the job for personal reasons, but was also angry. This guy said he went out at night to try and help a buddy who also ran aground. How fast he had to be going at night to run as far ashore as he went is unknown, he wouldnt say, but he was definitely hauling butt.
There is simply no reason to run over 5 knots in the dark. Especially near a shore or harbor, you simply cannot see well enough to avoid all the hazards, and sadly, accidents like this are the result. Even out in open water, floating logs or other water hazards can cause a great deal of damage if you strike them hard enough. At least in daylight you can see and avoid. Hard to see a black floating log at night.