EFX
Contributor
For those of you who are wondering how to signal going to a shallower depth since the thumbs up signal in OW means going to the surface immediately, the NACD recommends raising an open palm toward the surface followed by the numerical signal for the new depth. The open palm signal without a new depth simply means go a little shallower or get off the bottom.In my OW class I was taught the thumbs up signal meant going to a shallower depth. This signal could be followed by the number of feet or meters for the new depth. I have since adopted the NACD (National Association of Cave Divers) one-handed signals. In an overhead environment the thumbs up means to exit to open water immediately. This signal must not be overruled and needs to be returned by the buddy. In open water the thumbs up means let's go to the surface now bypassing any deco or safety stops. It also cannot be overruled and must be returned by the buddy. In both cases the buddy pair stays together throughout the dive.
There are a couple of advantages to using one-handed signals. For night diving you can shine a light on the hand used for signaling or, while one hand holds an object (ex. camera, knife, slate, light, etc.) the other free hand can signal without having to clip things off to have both hands free.