2.  Other units have a rear lens, the Shellicam does not.  Why?  

 

Our original prototypes did have a rear lens. During testing, we found that the rear lens was never used except to watch for leaks. Once we improved the reliability of the seal and housing, we were able to remove the rear lens. We also found that by using a rounded rear end, it allowed for softer "giant step" entries while diving. The rounded surface entering the water at high speed creates less impact and shock to the sensitive camera inside. The rear lens also allows light to get into the housing causing possible glare issues. Our housings are also coated internally with a flat black textured coating to minimize glare.