The CT-18 is one of our favorite to primary lights for technical dives. It's military grade aluminum casing, patented mechanical switch, and ease of use, makes it robust and reliable, one of the main focuses for technical gear. The 1800 lumens in an 8 degree beam punch through water and silt while still holding an impressive burn-time for its size.  The handheld version has a burn time of 7 hours! 

We typically run this light at the more conservative 900 lumen setting as it is plenty bright, and allows for the full 7 hour burn-time. The thicker the slit the more light refracts back, blinding you! It is a common misconception to want and run lights as bright as possible, especially for cave and wreck. 

NOTE REGARDING LIGHT CIRCUITS and RATED OUTPUT:

All Crelant/SUPE lights use constant current (continuous output) drivers; unlike other brands that use a variable output with 'Big' claims. What this means is that you will achieve full rated brightness until the battery reaches around 30%. Following, the light will dim to preserve the remaining battery life. 

A light that does NOT use a constant current output driver will begin to dim almost immediately. It will continue to dim as the battery is depleted and the voltage drops. This means that a light rated at 2000 lumens, will only be around 1500 (or so) within the first few minutes. Buyer beware of large output claims for the rated batteries. This is one of the main reasons why we recommend our lights in addition to the durability and quality.