Should…but remember they get hot…hopefully the resin can hold up to the heat (solid objects no matter the materieal will still have a thermal connectivity, how fast, that is to be seen, but plunked in the water, cooling “should” be adequate)…this is why I was saying something about
This is the 10W emitter…alot bigger than any XM-L
https://www.fasttech.com/p/1103509


Here is a “blue emitter” but it’s lumen output is MUCH lower than the above white LED
https://www.fasttech.com/products/1609/10001245/1103510-10w-180lm-470nm-blue-light-led-emitter
This thing is the driver for the above emitter
http://www.fasttech.com/products/1110706
It is already rated at 12vdc, the driver is there as a “regulator” but it should work just fine
Resin
http://shop.hobbylobby.com/products/clear-polyester-casting-resin-840462/
Transparent resin dye
http://shop.hobbylobby.com/products/blue-transparent-resin-dye-761676/
1” (25.4mm diameter) clear plastic PVC tubing
Solder the emitter to the driver, solder a lead from the driver to battery clips, maybe bend the wing/tabs up so they don’t poke out as far, slide all of it down into the clear plastic tube…mix up some light blue tinted resin, fill it up…let it harden/cure
plop it in a bucket of water, hook it up to a battery and see if
A. It makes a TON of blueish light that you want
B. see if it gets too hot it melts the resin/pvc and goes kaput
If it makes enough light…yay…win…if it doesn’t…might need more heatsinking
Good way to make sure the led is level is to do a couple pours, first pour to make a plug on the end, as it cures and get’s tacky slather the led in liquid resin, gently lower to harder plug till it nestles level, then fill it in the rest of the way, make sure you bend/kink the battery leads to give it some tension strength, don’t want to accidentally pull the cord out if it isn’t held tight enough by the resin
As I was saying with fiber optics, a few bits of shiny glitter or foil below the emitter might keep the light from just following the tube and shooting out the end without any side reflectivity
Oh you want a bling light to bolt up to your boat not a plunk sink down and bring the fish light
Might experiment with different mounds, maybe a square mold, then drill out the corners for mounting bolts…either or, that LED should be pretty darn bright
Reflector like the below, modeling clay to make a mold this way it give you a mounting option

