In Australia and New Zealand, wiring rules divide your bathroom into 4 distinct zones. These zones help determine what wiring and lighting you can have in each zone.

The 4 electrical wiring zones of an Australian or New Zealand Bathroom

 

Zone 0:

The Interior of a sink, base of a shower or bathroom.

Zone 1:

This zone extends immediately above bath, showerbase or basin as follows:

Bath (without a shower): Zone 1 extended from the top rim of the bath to the ceiling - or a height of 225cm for higher ceilings.
Shower over a Bath: Zone 1 extends in a 120cm radius of the fixed shower head connection point.
Standalone shower: Zone 1 includes the area from the vertical plane 120cm radius from the shower fixed plumbing connection between floor and ceiling, or to 250cm horiziontal plane above the floor (whichever is lower).

Zone 2:

The area limited by the vertical plane external to Zone 1 and the parallel vertical plane 60cm external to Zone, 1, and between the floor and the horizontal plane 225cm above the floor. 

Zone 3:

The area limited by the vertical plane external to Zone 2 and the parallel vertical plane 240cm external to Zone, 2, and between the floor and the horizontal plane 250cm above the floor. 

What lighting should you buy for each zone?

You should firstly consider ventilation in your bathroom, and include an enextration fan. Safety within your bathroom should always trump aesthetic appeal and the desire to attain decor trends.

For best outcomes, fix lighting in Zone 3 only, but where lighting is required in Zones 0, 1 or 2, it must meet the following zone rating:

Zone 0	Zone 1	Zone 2	Zone 3
Lighting rating must be IPX7 and SELV supply (extra low voltage)	Minimum IPX4 rating	Minimum IPX4 rating	Any lighting is suitable provided the room is well ventilated using an extraction fan.

 

Refer: Australian/New Zealand Wiring Rules AS/NZS 3000:2007