I'm a little concerned by this part of the Russian review:
"It is curious that during the presentation indicated that it can be used in the rain, but do not drop into the water. Let me remind you that the standard of protection IP67 suggests the possibility of diving to a depth of one meter for up to 30 minutes. At Galaxy S5 has built a plug for microUSB-socket, but there is no visible protection of audio jacks. From informal conversations revealed that the company specifically emphasizes that we should not throw the phone in water. It can withstand immersion standard IP67, but tightly closed lid will lead to leaks. The company believes that it will not be covered by warranty. All products with IP67 have the same notes in the instructions, they can not swim, they can not be lowered into the water."
What it sounds like to me is that while it is IP67, there are many points of failure (not snapping the back on properly, not sealing the charging port properly) and they do not want to encourage users from dunking it in water or swimming with it. So if everything is set up correctly, yes, you can submerge it. But they won't officially allow it or they will open themselves up to tons of warranty exchanges for water damage. Anyone who wants to submerge the phone does so at their own risk.