Not swimming in praise, but not drowning in disappointment either.
Personally I view this as a solid start to a prequel and midquel, essentially a whole second story playing parallel to Six’s.
This DLC is essentially the first chapter to this secondary story and is structured much like the main story chapters with one main villain to evade.
Set in the titular depths a lot of the terrain is very watery. Given the amount of swimming you have to do to traverse it as well as the controls being quite finicky it can get a little bothersome here and there if you have a low level of patience. However personally I didn't find it too bad nor did I need to redo individual areas that often. Still I can see some people getting a little frustrated with this DLCs gameplay.
In terms of time spent this chapter took me a little over an hour to complete.
On the whole I recommend this DLC if you enjoyed the main game and don't have too much of an issue with the slightly clunky controls.