Okay, adding some info to take away the mystery a bit...
This takes place in Egyptian waters on the Red Sea. Both boats are liveaboard diving safari tour boats catering to the wreck explorers.
The site is the wreck of the WWII transport ship The Thistlegorm, which is the single most popular wreck dive in the world.
While there is nothing on the surface and the video suggests that both boats are in clear open water, they are both in business around their "prize" which lies 30meters below.
The Thistlegorm is, pretty much everyday, the focus of as many as 20 such huge dive-boats at a time! So manuevering gets tight! It gets especially tight given that the way to anchour/moor in the area is for the head diver to dive the rode down and tie onto the wreck's superstructure!!!!
All this aside, The ship that the video is taken fomr the deck of was manuevering in to tie up and launch its divers while the other boat had cast off and was pulling away as one of the divers had been injured and they diecided to "run in". Apparently they did not politely sound their horn to announce that they were going to manuever under power in this nightmarishly tight anchorage...and you can see the result.
So not all is quite how it looks in the vid.
I am at home sick, and too ill to even use powertools and do some boat projects aroudn the house. Google hunting this down was my source of amusement for the day.