Caraka wrote:"" The ocean has a gradual shelf, a gradual slope, a gradual inclination, with a sudden drop-off only after a long stretch. The fact that the ocean has a gradual shelf, a gradual slope, a gradual inclination, with a sharp drop-off not just after a stretch: This is the first amazing and astounding fact about the ocean that, as they see it again and again, has the Asuras greatly pleased with the ocean."
I can't see the picture. What is a gradual shelf, a gradual slope, a gradual inclination, and I have never seen the ocean do a sharp drop-off?
When I see the ocean it is just water, like water in a jar. E.g. there is no sudden drop-off.
Oral literature uses repetition of words with the same meaning to emphasize a point not that they each specifically point to similar but separate things, the suttas use three usually, although the Abhidhamma uses seven.
so when the text you quote says "a gradual shelf, a gradual slope, a gradual inclination," this is referring to the continental shelf in the above linked image, with the sudden drop off being the continental slope in the picture, not that the slope in both are the same thing.