Chain drive on a ship engine - GIF

Chain drive on a ship engine.

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Previously:

CNC machining a ship propeller - GIF
Cargo ship breaks in half - video
How a ship transits the Panama Canal - GIF
Launching a ship with rubber airbags - GIF
Royal Caribbean Oasis-class cruise ship engine - photo
Salvaging a 50,000 ton ship by cutting it into slices
World's oldest intact ship - video and photo

Is the chain a connection between the engine and the prop shaft ? And, if so, why ?

I think that's the cam and accessory drive. You can see the crank and a rod...

Somehow, a ladder with oil dripping off the rungs is disconcerting to me.

The largest marine diesel engine made by Wartsila.
You can have a quick look here. https://youtu.be/7np9rhQmNTU