Hi Keyz,
You will get a mix of opinions and advice - all valid and all reasonable ways, so I will throw my 2 cents worth as well
In an area that will be subject to water, I personally would use Aquapanel instead of plasterboard irrespective if I were going to tank or not. Reason being if the surface that was over the aquapanel or the plasterboard failed and water got through, plasterboard will not survice for long, so even after fixed the dodgy grout or loose tile or whatever, it may be too late.
Aquapanel can be submerged in water and will keep its integrity, so in the same scenario,will dry out and be good as new again.
Worth spending the extra money on, I think.
On tanking, never used it, but the pros seem to swear by it as it means they don't have to go back for remedial work.
I went to a bookstore and asked the saleswoman, "Where's the self-help section?"
She said if she told me, it would defeat the purpose.