I took Courui D01 and made a new body and driver to use it deep down under water 
Here is just a picture + first swimming pool test.
I will describe the build in separate post(s)
Yes, that whale is me 
I wanted to have a strong, focused light to comunicate with other divers:
- full circle means both question and answer ‘everything ok’
- quick shake - ‘look at me’
- wide zigzag - ‘I have a problem… like out of gas etc,’
I have never shared a full story of this build so I thought this OL_Contest is a good way to do it:
I chose Courui D01 as a source for this project because of big reflector.
Step1: make a new thicker pill
Step 2: remove ~0,5mm from the bottom of reflector and solder XHP35HI onto maxtoch 26mm dtp board
First raw tests using iCharger106B as CC source:
Step3: Make a new body with M16x1 and M16x1.5 threads for piezo switch and cable gland
I have access to a very small hobby lathe
Here is how I make the holes:
Stay tuned ….
Interesting blast from the past, I have one sat here wondering what to do with, still remains the best shaped light I have. Great to see it being utilised.
The video however dates from 18 Jan 2016, so how can it be entered into a 2020 competition? As I understand it the entry should not have been started until the competition started - this year, or perhaps I’m misunderstanding something?
Also the raw test video is from 7 Jun 2016 and the underwater test from 30 May 2017.
Looks real good Mieciu. Whats the driver and battery source are you using?
The best cheap light for thrower mod Too bad they did not sell just the body…
Back to the subject:
Step4: - the driver
I couldn’t find any ready to run solution for 16,8V operation supplying 2.2A to XHP35 and also controlled with piezo switch.
The closest thing I found was a simple 1 mode driver bought on ebay from user mtolya
I started learnig arduino IDE to program the small digispark board(attiny85)
I wrote a simple code to generate 32kHz PWM and connected it to ‘enable’ pin of the IC from the driver.
Default 500Hz was too noisy.
Further code tuning gave me the recognition of long and short press signal from piezo button and reaction was only for longer press
Some pictures:
First dry tests
Step5: waterproof connector
The idea is to have a separate battery with only one socket used for charging and discharging.
I used :
* SKINTOP® MS-M-XL M16 gland (modified on lathe)
* Amphenol RCA connectors (M11x1 thread)
* AGRO #1017.52 gland (flashlight side)
* 4Audio LS2250 cable/cord (2x2.5mm2 with good insulation)
Pictures:
Step6: final assembly, tests
Nice you learnt yourself to program. Thats black magic to me. 
Mieciu , very sweet mod on a light you will be using in a dangerous environment underwater where your life may depend on it working. 
Very good underwater video showing it being tested, and all your videos showing machining, electrical testing and assembling.
Fine job on you competition build