Water from exhaust on cold start

[PLP]

Well... could be... it is possible to accumulate more water.

Imagine, if you start cold, rich mixture, cold exhaust, all water will condense. Until higher revs or warmer temps, the moisture will stay inside. Do it twice or so and you can fill the exhaust with a lot of water.

At some point you will puke it. If the water is gone and does not come back, you are good.
If that was the coolant - well, you would know after first warm up.
Let me put it this way - if water can get through (to the cylinders) exhaust gases will, too. At much greater rate.
Then, you get overheating, pressure in the expansion tank... you know the drill.