Most of PSU, if you press the TEST button, ignore the water protection.

If you dont have response, need to divide the problem :
1 - Do you have a ammeter between PSU and tube ? there is usefull in this cases, when you press TEST, the ammeter have to indicate something between 4 and .. 30 mAmp
2 - The PSU have power ?. Most of them have a led
3 - laser not fire, ok, you see the laser tube ? or just the laser head ? there is 3 mirror in the middle, the first mirror is the most exposed and maybe,maybe is damaged
Martin.-