This is not true. THC is not water-soluble so it cannot get lost in the water pipe. Some cooling of the smoke or vapor does happen, and when that happens some of the cannabinoids condense and stick to the water or glass. This does make the hit slightly smaller, but the coolness of the smoke or vapor is so much better for the lungs that its worth it to sacrifice just a little to be kinder to your body. One thing to note is that smaller hits are actually way more efficient as your lungs can more readily absorb more of the vapor. We like to say mass micro hits are the way to go for efficiency and being kind to your body. You only get one.