The large pipes on deck, coupled with the lack of cargo hatches or cranes, makes this one a tanker. The small number of pipes, and their relative large size, means this ship probably carries only one type of liquid. I'm guessing oil. It's not a particularly large tanker so it is likely used to work smaller fields and ports.
Sea - Cargo 
These pictures are often commissioned by news agencies. Maybe there was a ship stranded or something and a news agency commissioned the pictures.
I checked lists of lightships and this doesn't seem to be one. They are much smaller anyway.