You'll have to read it all the way through to get to the point. I'll sum it up for you.
- Scientists of today has found that something about the way oceans work mean that they can be described as two layers (one top, one bottom).
- Where these two layers meet, deep into the ocean, there are a lot of turbulence and waves (or billows). This explains certain optical phenomena.
- People living thousands of years ago couldn't possibly find this out because there weren't that many deep sea submarines around back then.
- The Koran says something (Waves on top of waves) which can be interpreted as describing this phenomena, and since the knowledge couldn't have come from man, it must come from Allah.