Silence underwater, deep, very deep - if you want, long, very long - if you want. With rebreathers the possibilities are endless.
In comparision however to open circuit you need to have more knowledge, extended dive skills and alot more equipment.
There are two different rebreather systems: SCR - semi-closed rebreathers and CCR - closed circuit rebreathers, both either manually or electronically controlled. Here´s a quick overview of the different brands on the Market: JJCCR, Revo, Hollis Prism, Hammerhead, Liberty, APD, Megalodon.....
Rebreathers - a facinating way to dive.