I am just finishing my OW certs now - FUN, FUN, FUN!
You do not have to be in great physical shape to dive - sure, it never hurts you, but you don't need to be super fit to dive.
I agree with above others...look around at what other divers are using for gear - and look at various mail order web sites. There are many great brands and models out there...I found this really great UK scuba web site that tests all kinds of scuba gear, as does Rodale's Scuba Online Magazine...they can be very helpful in selecting gear. See:
Anyways, if you are concerned about your physical condition, try and do some walking every day or 3x per week. Great for your heart and lungs as well and the condition of them greatly affects your air consumption, heart rate, and overall health.
BC's - 3 styles to choose from:
*Back plate and wings
Most people go with jacket inflation BC's, although some like Back inflation BC's. Personal choice.
Many 'tech' divers (thats divers who dive deep - deeper than the usual sport diving of say, 100 ft) cave divers and wreck divers. They choose to use more streamlined, less bulky gear that is more simplistic is design - called backplate and wings. Some of these are Halcyon, OMS and Dive Rite. All of the them have web sites. Popularity is slowly gaining on backplates and wings, since they are modular in design, so itís easy to add/change components as your diving career grows. Say if you like to dive doubles (2 tanks) someday, or get into 'tech' diving.
As far as Jacket and Back inflation BC's - there are SO many good brands, Tusa, Mares, Genesis, Scubapro, AquaLung, just to name a few...
I have thin legs and I had better luck with my US Divers Rocket fins (or Scubapro Jets) than with a longer blade that was on my US Divers 'Blades' - they were powerful on the power stroke, but because they were longer in length they made my legs cramp. The shorter fins don't do that to me. Proper scuba technique is as important in this sport as in tennis, golf, etc. as it allows you to conserve energy by swimming properly. We also have several kicks that if your legs tire while doing one, switch to the other and employ different leg muscles to rest the tired muscles.
My BEST advice is to those coming into this sport is:
1. Do your homework on gear from many of the great mail order web sites (such as this). Look at test reports, go to the manufacturers web sites and look at models, styles, even colors of gear. No matter what local dive shops say, internet mail order of scuba gear IS getting big, and for such reasons as selections and prices. You can save hundreds of dollars purchasing from sites such as this, on quality WARRANTIED gear. WARNING - not all Internet mail order sites sell gear with FULL MANUFACTURERS WARRANTIES - they purchase some of it via 'bootleg' methods - thus meaning you are purchasing gear w/o warranties! NO KIDDING! This is LIFE SUPPORT gear folks, so be careful! Buy from those will SERVICE and care you - the customer and diver!
2. Observe what others are wearing. Ask WHY they chose brand X over Y...don't purchase just to be 'trendy'- but in this sport, you find many favorites and patterns of gear - and for good reason - it works!
3. Get out there and dive, dive, dive...have fun, dive safe and smart and STOP WORRYING! As you get more experienced, all this begins to fall into place! The more you dive, the better you get at this!
4. And above all - there is NOTHING to be nervous and anxious about in this sport. There are NO monsters down there looming in the dark to eat you up. Visibility is many times much better than you'd believe. I used to equate poor vis with scary diving - NOT SO! My very first checkout dive cured that fear - even in 1-2 ft vis conditions, it IS NOT scary - you simply swim out of the silt up that you or your dive buddy's fins kicked up - or simply sit tight and wait a few seconds. Its is not claustrophobic at all, and its so cool and fun you can't imagine yet! But I can say this - for 99% of newbies - once you hit that water and descend - your hooked! Itís a whole new world to see and experience down there!
Most of all, dive safe, have fun and join DAN (Divers Alert Network!