Hey JBD,
If you are the owner of your very own integrated life preserver (like me!!!), then doing a surface dive may be your problem. I float like a cork; in fact, during my Float for Dive Master I kept my hands above water for the entire time
not just the last measly couple of minutes. The EASIEST method to freedive, (at least for me) is to take three real quick & deep breaths (NO MORE- see Mario's note on apnea & diving), bend at the hips (so your legs are parallel with the surface and your torso is pointing down). Then raise your legs into the air and let their weight push you down. A few kicks and a stroke or two (NOT a DIR thread here, so don't get excited) and you will be there. Use a L-O-W volume mask with a nose purge (cheating is OK) and gently float to the surface.
BTW, my Dive Master "final" was for two of us to descend to the bottom of the pool with one regulator off. Then we had to exchange all of our gear, all the while buddy breathing. Thought I was going to die, as I am very inflexible (my joints, Chester) and just LOVE to breathe. I got my DM cert, and am still alive to recount the tale, so I believe that most people can do it. It just takes practice, the right mental attitude, and an affinity for pain. :tease: