"Omega redesigned the Seamaster 300M Professional for 2018 and below are some hands-on shots to give you an idea of what it looks like in the flesh.
The Seamaster 300M Professional case features Omega’s famous twisted (lyre) lugs and measures 42 mm x 13.56 mm and each version now comes with a ceramic bezel insert and a Ceragold or white enamel filled diving scale.
At 300 meters the watch achieves 3 times the water-resistance required to be an ISO 6425 dive watch. It also features a helium-escape valve for saturation diving, which is not even a prerequisite of the aforementioned standards."
https://www.professionalwatches.com/seamaster-300m-professional-dive-watch-hands-on/