The cases of Skeleton (AVE-64) and Tourbillon (STL-117) are made by 316L stainless steel (military level), it is extremely anti-corrosive.
Also 316L stainless steel is extremely hard.
Hardness, Rockwell B ≈ 80
Vickers hardness ≈300
Sharp case shape design reflecting the prefect aerodynamic design of the Stealth F-177, each cut is done by the highest precision of CNC machine produced in single piece at a time.
10 ATM (100 meter) water resistance. This standard of water resistance is extremely high amount tourbillon watches and mechanical watches.
Don’t worry about entering water in daily lives.