I'm pretty excited about this camera, and I would be surprised if we don't see UW housings for it... Here's a great video demonstrating that not only does it have 5 axis IBIS but it blows the Olympus OM-D E-M10 Mark II out of the water. That said, these types of test can usually be rigged in the favor of ones strengths vs. weaknesses, but nonetheless it looks very promising.
Looks like the lens on the Oly is longer / extended.
Apart from that it's cool that Pana now has been able to include IBIS.
Let us hope that GH5 will also iclude IBIS.
I have no loyalty or biases as to Panasonic vs. Olympus. I would use whichever brand appeared to offer me the best product for my needs at the time I was buying. As to this camera and underwater use, it appears the max flash sync speed is 1/160.