First off, don't believe every fucking thing you read or hear ESPECIALLY when it's from other stoners who heard it from someone else who made it up....

Ice in your bong cools the smoke making it easier on the lungs..

That's the whole point of smoking from a bong anyway...to cool the smoke and it acts as a filter because alot of crap is caught up in the bong water as well...

There is some debate about whether or not you get higher with or without a bong or with warm or iced water or which filters crap out better but doesn't get you as stoned etc. etc..

For me...cooler smoke from a water bong is the easier on the lungs and still gets you high as balls...