Blue Grotto is not only among the world’s most popular recreational diver training sites, but it is also a popular site for students in tech and rebreather courses. You will frequently see students and divers at the Grotto using double cylinders with dual-orifice isolation manifolds.
These are very different from the single-cylinder yoke or DIN valves with which you are already familiar. This three-minute video will explain what isolation manifolds are, how they work and why so many cave and technical divers use them.
Isolation manifold use is one of many things you must learn to become a cave or technical diver. This may interest you, or you may just want to stick with the familiar simplicity of single tanks and valves. Either way, it is nice to be informed.