Step by Step Instructions:

1. Build the middle part of the fish’s body (which is called the trunk) by creating a vertical standing rectangle box using ten small equilateral squares. An alternative would be using four of the 2-square rectangles and only two of the small squares.
    
2. Now create four trapezoid shapes on both sides of the trunk. Connect the two trapezoids with three small squares. These are the head and the tail. You can use 12 small equilateral triangles and six small squares. An alternative for the small equilateral triangles would be using four trapezoid tiles or a combination of four diamond tiles and four small equilateral triangles.
    
3. Use four small equilateral triangles to form the mouth of the fish in the form of a small pyramid.
    
4. Build the Caudal Peduncle of the fish (the thinnest part of the fish’s body before the tail) by forming a 3D triangle using two small equilateral triangles and a small square. Note that the bottom part is open. Adding a small square at the bottom would make the build heavier and unstable. Connect four small right-angle triangles to form the tail fin (called Caudal Fin). The Peduncle is like a stem for the fins. It acts like a motor and the fins are like the propeller. The strong swimming muscles of the tail are found in the Peduncle.
    
5. Connect two small right-angle triangles on the back of the Fish. These are the Dorsal fins, which help maintain balance while swimming.
   
   
6. Attach two Isosceles triangles, one on each side just behind the Fish’s head. These are the Pectoral Fins which help control the direction of movement during locomotion.
   

   Have fun learning while playing!