From further descriptions, it sounds like visibility is basically zero underwater in the area. In one article, it mentioned that there is only a brief window when the tides change direction and visibility improves for a short time, measured in minutes.

A small number of divers are able to enter the ship at other times, it seems. Another article mentioned that even inside the ship, visibility is zero and they have to literally search each compartment by touch, like a fire fighter searches a smoke-filled room for victims. Must be very easy to get disoriented or have their air hoses and communications lines tangle up.

So, it sounds like once the ship started taking on water, even a very strong swimmer would have a heck of time trying to find their way out of the interior of the ship under these conditions unless they knew exactly where they wanted to go and could visualize that route with the ship turned on its side or upside down.

It does serve as a reminder of the logic behind the advice when boarding a commercial flight to count the number of seatbacks to the nearest exits.

The same article mentioned that many of the bodies found within the ship have broken fingers, probably from frantic attempts to escape as it took on water. So sad...