hj, I am very new at this, and quite square too. Here is my take though.
I use a Sunnto dive watch, the d3 or mosquito. They will measure your dive time, and on arriving on the surface, automatically start to count that surface time, whilst still displaying your recent dive time in the bottom right. Sorry if it sounds confusing, but just look for relaxing at least 2x the past dive time. Even after 5 dives it will become very easy and natural to do.
If dives exceed 15m, or you feel that the 2x is still not enough, maybe because you are exited, cold, tired, current, your body should tell you by the crappy dives. In this case back off to 4x or even more. YMMV.
If you listen really hard to your body, you will start to know when you are ready again, which is quite a bit after you initially feel ready. You will see beginners doing 1x dive/surface, because the think they are good to go. It may take 6 months of diving to be able to listen carefully enough to really know though
we demand a full trip report + photos!
