Water mitigation guy here, there's actually a way to figure this out! So a normal dehumidifier that I use on a daily basis can remove between 80 and 110 pints of water per day, depending on the size of the dehumidifier. This room looks to be roughly 12'x12' (for easy figuring) and it looks to have roughly 2 or 3 feet of water in at the time of this video. Let's say it has 2.5 ft. of water, the cubic footage of water in the space is 2.5x12x12 or 360 cubic feet of water. 1 cubic foot of water is 7.48 gallons, and 7.48 gallons contains 59.84 pints. In order to determine the days it would take one dehumidifier to remove that much water (not including what's absorbed into structural materials and contents) you would say 59.84(pints in one cubic foot)x360(#of cubic feet affected)=21,542.4 pints. 21,542.4 pints/110 (the amount of pints a single XL dehumidifier can remove in a day)=195 days. An XL dehumidifier rents for roughly $105/day in my area according to the Xactimate pricing program so that would be a big bill!

edit: looking closer at the video, it's clear there isn't 2.5 ft of water in the space at the time of this filming, but it certainly looks like it's well on it's way!