Watch OS 10 - Water Lock Gone?

Prior to last nights update to watch OS 10 I was able to activate a water lock function on my Watch SE which was helpful while working out as it prevented me accidentally pausing the workout unintentionally etc.

Since last nights update - that option has vanished and I can no longer see any way of locking the device - the only options available now are end, pause or segment.

Have tried pressing and holding the crown, the side button in any and all combinations with no joy.

Has this functionality been taken away or am I missing a way to do it?