DevonDiver's quote is great advice, and I tend to follow more in line with 00wabbit and DivemasterDennis above, especially if I'm diving with someone I've never been underwater with before.
And I'll tell you, after many years of diving, a simple buddy check - or a more in depth check as already mentioned above - BEFORE jumping into the water has prevented many problems and is the best segue into a great dive, which is what we strive for to start with, right?
This is still true today: Most all dive accidents and fatalities can be prevented on the surface.
---------- Post added April 24th, 2013 at 08:49 AM ----------
00wabbit, not only have I seen almost the exact scenario depicted here at our local fresh water hole, while completing a dive recently, I observed a diver enter the water fully geared up with his FRONT drysuit zipper partially unzipped! Indeed, his dive was cut very short! What was worse was that his dive buddy had ALREADY DESCENDED, leaving him to struggle on the surface while he tried to exit the water...... Here's your sign.....