Hydrofoil on KSP 1.9.1

But... Why in KSP 1.7.3? I wasn't going to probe 1.9.1? Well, I did. And got this.

The freaking thing just took off and reached 5K high at Mach ~1. :/

I don't know exactly what's happening, but apparently wet fuselages and wet lifting surfaces lose drag. And perhaps weight?

(more on the following pictures!)