Sidemount?  Isn't that for Cave Diving?

Yes, and No!

Think on this. Gas shut down drills are much easier in SM.  Gas monitoring is a matter of glancing down at the gauges in SM. Trim is better and more easily achieved in SM. Your back is flexible still in SM! No doubles, manifold or bands to buy in SM.

It doesn't get much cooler than this! Sidemount plus stages.

Technical Diving- Sidemount