Why is apparent depth dangerous for swimmers?

Apparent depth is dangerous for swimmers because 
 When you look vertically downwards into a swimming pool full of water the bottom  seems closer than it. If the pool is really deep and it doesn't look deep to you that's not good cuz if you don't know how to swim in deep water you might drown.

Hope this helps ;)

Ihope you get it right bro

You yeah with the side of the yeah with a little bit of yeah.