Two people are sitting on a rock looking off into the distance.
The diver is swimming up to the water surface.
It says the two people are sitting, so one of them cannot be diving to the waters surface.
THE DIVER IS  SINGLE PERSON AND NOT TWO PEOPLE AND THE DIVER CANNOT BE SITTING ON THE ROCK AND LOOKING OFF INTO THE DISTANCE
The subject is either a diver or two people. The subject is either swimming or is sitting.