Rebreather course.

Next month I am visiting Sharm (Egypt) to do a rebreather course with TDI (

From Wikipedia:

A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycles exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where humans cannot safely breathe from the atmosphere. In the armed forces it is sometimes called “CCUBA” (Closed Circuit Underwater Breathing Apparatus).