Paper on CFD testing of a boxfish
 

I know some of you are going to find this interesting :
https://royalsocietypublishing.org/d...rsif.2014.1146

Here is a very small section of the study
QUOTE
bodies under the same CFD simulation settings result in a drag coefficient of about 0.15 at a Reynolds number of 75 000 (S. Van Wassenbergh 2014, unpublished data). A medium-sized adult trout Oncorhynchus nerka without pectoral fins at a Re of 5 × 105 had a similar drag coefficient of 0.155 [25]. Although boxfish clearly outperform true boxes or spheres at a similar Re (Cd of 1.05 and 0.47 [16]),

There are also several CFD images in the study that you may find interesting.

Boxfish pulse and glide?

Lol - absolutely !

Reynolds number
 

Anything measured below Rn 500,000 would be sub-critical, and meaningless for a road vehicle larger enough for humans to fit inside.
If 5 X 105 means 5 X 10-to the fifth power, then Cd 0.155 is of value.