What did Megalodon Look Like?

 New study conclusions: 

Body forms of extant lamniform sharks (Elasmobranchii: Lamniformes), and comments on the morphology of the extinct megatooth shark, Otodus megalodon, and the evolution of lamniform thermophysiology

Phillip C. Sternes, Jake J. Wood & Kenshu Shimada

One proposed comparison shape (marked "Free to Use and Share' on Creative Commons)

This is a really good example of what we can and can't know from incomplete fossils. Sharks, like my favorite fish Dunkleosteus, have a cartilaginous skeletons that rarely fossilize.  

Did they look like great whites? Did they look more like some other extant shark? 

We don't know. 

"...all previously proposed body forms for O. megalodon should be regarded as speculations (Figure 9) because there are no scientific means to decisively support or refute the accuracy of any of them. Any meaningful discussion on this specific topic would require the discovery of much better-preserved fossil specimens than what are presently known in the fossil record of O. megalodon."

Darn.