my wife and I recently went to Cozumel and did quiet a bit of snorkeling. I am a good swimmer however my wife is not at all. We both want to get certified in scuba and my only worry for her is the treading water test. What do you recommend in preparing her for this. Thanks

[At some point prior to certification
the instructor must document
that Open Water and Junior
Open Water Diver candidates
complete a:
1) 200 metre/yard continuous
surface swim and a 10-minute
swim/float without using any
swim aids.
OR
2) 300 metre/yard swim with
mask, snorkel and fin and a
10-minute swim/float without
using any other swim aids.
If confined water conditions
require students to do this wearing
a buoyant exposure suit,
students must weight themselves
for neutral buoyancy. Scuba
Divers must complete the 10-
minute swim/float only. All
student must demonstrate that
they can comfortably maintain
themselves in water too deep to
stand up in prior to Open Water
Dive 2.

Increased physical activity and continued snorkeling should help.

Well, the requirements are different with the various organizations.
I suggest swimming more, and practice the tread water test if that is what you are concerned about. Build up endurance. Go running, and biking to build up endurance if you can not get into a pool.
Good Luck, you will really enjoy diving