TLM Studios is a German developer that most people here probably do not know. They started with a Train Simulator module featuring the Subway in Berlin, then showed two independant subway simulators that are of very good visual quality (I know the one that again visits Berlin, the other was for The Path in New York), they published a real-time role playing game (Sunshine), and their last strike was a Bus Simulator for New York.
They now work on the simulation of visiting the Titanic down there in the dark, with the player sitting in the 3D-modelled interior of the research submarine that gets launched from the surface ship, and once arrived there he will be able to steer a remote controlled diving robot into and through the wreck, searching for treasures and unique items and seeing the Titanic's glorious interior that now is hidden under corroding rust, sand, corals. The graphics are photorealistic.
http://www.tauchfahrtzurtitanic.de/
The site has a minor display issue, at least for me. at the bottom, you can click on screenshots, at the left top, partly hidden, there is a small menu where you can access videos, and some project data. the first video has much text in the first minute, you may want to move thr slider to the right until the clips start.
Can't say anything on gameplay, but the visuals look like being taken from a James Cameron docu on TV!