It depends on the situation. When serving as a boat officer in a combat area, yes, they wear a pistol. In some small ships all personnel are issued a side arm in combat situations. Navy officers stationed with the Marine Corps will be expected to be armed (doctors and chaplains excepted).
It depends on the local department regulations. Locally to me, city officers carry a Sig 229, and county officers carry a Beretta 96D. Glock has a pretty large percentage of the market, as does Sig.
depends on what you mean by officers (military, navy, police, airforce) but 2 very common WWII revolvers were the webley and the enfield in various models
The official sidearm of the US Military is the Beretta M9, 9mm Parabellum pistol. I would imagine that at the level of operations the Navy SEALS are at, the individual can carry the sidearm of their choice. This may well be the M9, but another popular pistol is the M1911A1, .45ACP which was the official US Military sidearm from 1911 until the 1980's (before the M9). I don't know of any restriction regarding their choices. I doubt many would carry a .22LR Derringer though :)
Smith & Wesson promoted their .38 caliber revolver as the best sidearm for army and navy officers.
They will have some determination in what they use as their backup piece, but they'll be limited to whatever the department issues as their service sidearm.
None
Colt .45 ACP
Colt .45 ACP
sidearm and a rifle.
Absolutely - Navy EOD teams have officers in charge just like any other unit.
CCW is shorthand for "carry concealed Weapon". It generally refers to a sidearm that is suited for concealed carry. These would be smaller and flatter than most sidearms. Nearly any sidearm CAN be carried concealed, but some are more readily caried in that fashion.
At the end of August 2007, there were just under 52,000 officers serving in the US Navy.