Requirements:
-Neutrally buoyant
-Fully autonomous
-Capable of S-turns, barrel rolls
-Guidance system
-Capable of sensing and hitting 10 Hz LED strip on the far side of a pool
-Launched out of 200 PSI air cannon
-$100 Budget

Story Time
I was the lead for electronics and programming on this project. For as long as we had hardware, we had been plagued with electrical issues; we kept burning out the
motor controller boards. It wasn't until the night before the final test that we found out that the wrong stepper motors had been ordered and the system was pulling too much power. At the point of discovery, we had one port on one drive functional. After some frantic thought and evaluation, we determined that we could substitute the fin steppers with smaller Mercury motors and wired them in reverse. The collective current draw would be less than the maximum on the H-bridge, and because they were wired in parallel, they would receive the same voltage. However, because they were wired in reverse, the motors would spin in opposite directions and we could achieve the required orientations for both the barrel rolls and S-turns. We worked from 9 pm until 2 am rebuilding and reprogramming the system, then from 2 am to 6 am testing the system. After several hours of rest, we returned at 8 am and continued testing until our final pool test at noon.

Final Design
-PVC body, 3D printed tail, acrylic head
-Stepper motor controlled fins
-LiPO Battery, ESC power system
-Arduino microcontroller
-Digital PID controller
-Light sensors
-Gyroscope
-Fully autonomous