Anyway, the short answer is: No. Altimeter watches need a small "port" that basically lets in air (and air pressure). That largely eliminates a watchmaker's ability to waterproof the thing to dive standards. Most altimeter watches, such as the Suunto Altimax ($169; www.suunto.com), are billed as water resistant, but are not meant to be submerged in any more than a foot or two of water.
So, it looks like two watches for you, bucko. The Altimax is a good barometer/altimeter watch, although for years I've preferred the Vertech Alpin II ($160 at Campmor.com). That's due in part to its exceptional accuracy. I've hopped into my car at 375 feet and 12 hours later walked into Camp Muir, 10,100 feet, with the Vertech reading each increment dead-on. But, I also like that the Vertech reads rate of ascent/descent in feet per hour, which is much more useful than the feet per minute most other watches use (although that may be better for you if you're leaping out of an airplane!).
For a diving watch, it's very hard to top the Citizen Aqualand Duplex ($279; www.citizenwatch.com). Damn, it's a handsome beastand waterproof to more than 500 feet, which oughta be more than enough.
Just be sure to take the Vertech off before hopping into the water...