There is a group who do  weekly training sessions at Beatty Park.

http://www.wadivers.com.au/forums/viewtopic.php?f=17&t=3295

Get your self a bike mate.

I use to run but due to playing footy my knees played up and I nearly was in trouble with them.

I got a mountain bike to keep going and it just as good without the pain .

Longer breath holds wont happen over nite but if you keep to a simple fitness program it will get better.

As try boxing as its a great cardi workout.

Learn breathing exercises as you will be surprized how much more air you can get in when you learn these.

Hope that gives you abit of help,

Craig

you need to train your muscles to work with less oxygen.  basically do general cardio and youll do just that.

is the very best exercise you can do, not only from a working all muscles group point of view, but it will blow your lung capacity out substantially.

Yeah I recommend joining a club and you will learn alot.

I play underwater hockey, i'd say that's the best form of watersports you could do. Plus building up your cardio fitness. Also do static breath-holds in the pool, and dynamic sessions. You must have a partner spotting you though. Dynamic sessions are good to perfect your form and sort out the comfortable way to propel yourself while using the least amount of energy/oxygen.

 I also do breath hold tables in 2 forms, O2 Deprivation and CO2 tolerance. One will increase breath hold times gradually while keeping rest periods constant, the other is visa versa.

Nothing beats actually diving too. Getting used to being at depth. Controlling the very uncomfortable reflex you'll get when both at depth and at low O2 levels.

If you have a good static breath hold but can't find the bottom time then you will need to sort out all of the above. My cardio is up the sh*t which means good bottom times straight out of the boat but not so good after a swim.

as a beginner, like dd83wa said, nothing beats diving. Try string a cpl of days together snorkelling for crays in the shallows and you'll notice a heap of improvement.

Or otherwise you can go one of these but your workmates might think you're smoking ya missus lady wand

http://www.powerlung.com/region/us/

Cray snorkelling is great exercise and breathhold practice. Its amazing how much extra air you can find when you latch onto a good one and then the wrestling starts.