Until you drop the phone, the reservoir holding the water breaks and fries the internals due to water damage.
I'm not saying this is likely to happen, but I would be very curious to see exactly how many cases of something similar pop up after this phone enters the wild. Liquid cooling on a mobile device is a neat concept but doesnt seem like a very smart thing to do.
It seems to be the same heatpipe that was found in the Z5 Premium recently. It's not actually like if they were using watercooling

In fact, I'm pretty sure that it's now a part of the S810's recommended integration by Qualcomm to prevent the SoC being as warm as it usually does.