Girls, lifevest is a must and you will be expected to swim on your back to the other end of the pool because of your lifevest. You wouldn't be able to swim on your front and non swimmers shouldn't have any trouble except to kick your way to the end of the pool.
As for contact lense users, do take precautionary actions and really, it's more about common sense than anything else. If you have lenses and you think you need them, you can jolly wear them for the dip together with your goggles. If you think you can still see without the lenses, by all means.
The height from the mock plane to the bottom of the plane is roughly 4 meters high. Remember, this is water confidence test and not about if you can swim over to the other end. If you fail to jump off, you know you're not going to make it through the next round.
Last but not least, please, please attend the interview first before you start to worry about anything else except for the 1st round and the 1 to 1 interview. It doesn't make sense for yourself to go through the pressure cooker when you don't even make it past the first round. It's good to prepare BUT prioritise the the stages yeah.