Underwater 12v XPH70 Build for Boat

[efine]

Idea is to build an underwater light for a boat.

Basically I want to create my own version of this:
https://www.amazon.com/Waterproof-Brightness-Underwater-Viewing-Swimming...(link is external)
Example of someone trying to do this but doesnt look like they accounted for heat, or the latest LED tech:
https://teamtalk.mastercraft.com/showthread.php?t=60312&page=2

Constraints:
Battery

• Voltage Source = 12v battery (assuming volt has a range of 12v with engine off to 14v while engine running)
• Battery Source: Interstate Batteries | 24M-XHD

LED Option 1: XPH70.2 12v
Cree XHP70.2 P2 5700K on DTP MCPCB (mtnelectronics.com)

• High lm/w option with lower heat than 6v version due to lower current draw
• BUT, I cant figure out a driver to use. If the driver reduces the source volts, then the LED wont work while the engine is off, right?
• 17mm MTN-MAXlp HP 1A-5.5A Low-Profile Buck Driver - 5V-18V (mtnelectronics.com)
• Is there a cheaper driver anyone could suggest?
• The datasheet says 1050mA preferred current, and 2400mA max current. But I've seen other threads where people run these much higher. Is it ok to aim for 2400mA or should I aim lower? (assuming good heat management)

LED Option 2: XPH70 6v
Cree XHP70 N4 1A on 16mm / 20mm DTP MCPCB (mtnelectronics.com)

• I could use a buck driver but then I have a lot more heat generation
• $5.21 26mm 4500mA 1-Mode LED Driver Circuit Board for Flashlight DIY - for Cree XHP70 / 6-15V at FastTech - Free Shipping
• Data sheet says 2100mA preferred current, and 4800mA max current. Which one should I aim for?
• This forum has a graph showing amps/lm & volts Cree XHP70 up to 4022 Lumens and XHP50 up to 2546 lumens - Multi-die leds. | BudgetLightForum.com

Construction:
Option 1: Water cooled

• LED covered with clear epoxy
• LED on top of aluminum heatsink, attached to the outside of the boat, in the water
• Hole cut in boat for wires

Option 2: Air cooled

• LED against inside boat wall
• Heatsink behind LED, air cooled

Option 3:

• Boats have a 1" diameter drain plug in the back underwater
• Could leverage that as an attachment location that doesn't require drilling holes

Thermal Heatsink Calculations:
- Lifetime Case Temp est: 100C
- Ambient temp ~ 30C
- Vf1 =12.6v | Vf2 = 6v
- If1 = 1 – 2.5A | If2 = 2 – 5A
- Efficiency ~ 70%
*HeatSink Thermal Resistance for 12v&6v is ~ 3-7.5 C / W
or 9 – 23 watts needing to be dissipated*
Formulas
dT = Case Temp – Ambient Temp
Pe(W) = Vf * If
Pd = W * Efficiency
Rth = dT / Pd
https://www.led-heatsink.com/thermal-calculation

Summary:
- Can I use the 12v Led with 12v source? If so, what driver should I be using?
- What driver should I use if I cant use 12v and have to use 6v LED?
- Any ideas for water proofing an LED?
- Any suggestions for very flat heatsinks, so it be as flat against the boat wall as possible?

Thank you!