Check out my other fish https://cults3d.com/en/design-collections/BIONICFACTORY/all-fish-flexi-project

A fully flexible tuna fish. You can pause the last 3 - 4 layers in the 3d printer and change to any other colour. I recommend printing the bottom part lighter and the top darker, so maybe the bottom yellow and the top blue or white and grey, but don't do it the other way around. I recommend printing the original size or printing the object larger.
The fish is immediately flexible after removing it from the mat .It is always folded from two pairs of clamps and this makes it stronger

I use my own more laborious technique where I get 2 mm detail on the top :P

          print setting 

2-3 walls 3 bottom layer 3 TOP layer 20 % infill
turn off supports ! TURN ON "ironing " in slicer on top layer

I recommend printing the original size or printing the object larger. !

Object size : object size - X - 111 mm , Y - 79 mm, Z - 12 mm