water cooling would add more complexity to install + temperature of antifreeze would be actually heating the LED. My radiator temo is around 70C there is no point of injecting that temperature to LED in fact it would be the same as leaving LED without any heat-sink at all. Fan we selected is industrial grade (it is not water proof but it is not expected to install module outside the car. Module should be housed under main headlight lesne. General moisture build up and vibration should not be a problem. So far i have same fan in my test setup and it been more then a year and no problems problems at all.
If you need more durable underwater type of led module then you need cooper based hit-sink and no fan at all, problem with that is cost of production is $300 per part :)