If you haven't dived in a while whats the best thing to do before you get back in the water, how long is too long out of the water? Should you do a refresher or a skills review, Should you do an equipment check, a weight check, read your training manual again or do nothing and just book onto a dive and get right in the water ?
These are all real questions and perhaps something that you might not think about in too much detail after a short (or long) break from diving but is certainly worth some consideration.
The question needs a bit of clarification before it can be answered, because its not a one size fits all reply. How long is a while? This needs to be answered first and It largely depends on you. The PADI recommendation is 6 months as a minimum which suggests anything less than 6 months should mean you're OK to get right back in from where you left off. However, there are many variables so it might be a good idea to refresh your skills first anyway.
If you completed an introductory dive course such as the Open Water Diver course, and haven't dived since, even a gap of 6 months might be too long for you to get straight back in the water without any additional activity. Most people will have forgotten some simple tasks in that short time, (BWRAF?) but more importantly the safety skills and procedures that were learnt may now not be as fluid or even there at all. Practice makes perfect, and when you learn something in a few days and then don't practice at all for a few weeks (let alone months) will see a huge drop in knowledge and skill performance. Add into that a bit of pre-dive nerves, buoyancy skills and situational awareness, you might have wished you stayed on the beach instead!
If you are a more seasoned diver and have more experience you might think that 6 months is nothing and getting back into the water posses no problem at all. While this may be true for your confidence and overall readiness to get in, you may be overlooking some simple factors that could make your dive more enjoyable. Do you remember your correct weighting for this dive, Pounds or Kilos? are you wearing the same thickness of suit, or the same size and type of cylinder? You can easily overlook any one of these and cause yourself to have significant problems with buoyancy control, comfort and ultimately safety.
Keeping an up to date log book is one great way of helping you out in this situation. Just a quick look back into the dives you have done will give you a good indication of what you did last time, how much lead you wore, what thickness of wet suit, size of cylinder etc and will help you plan your dive properly first.
One thing your log book wont be able to do is practice your skills for you though! So it is always worth spending time reflecting on those skills that are important, or even the ones that make you feel nervous and making sure you practice them in advance of any dive trip. You don't want to be getting ready for a boat dive and realise you've forgotten some basic kit set up or buddy check procedures.
Before joining any big dives or dive trips, make sure you have had the time to refresh the basics and get back to being comfortable in the water. This could mean one shallow dive, where you re familiarize yourself with the equipment and tell your buddy/guide/instructor that you would like to practice buoyancy control or maybe mask clearing before you go any deeper. Or it could mean going back and practicing in shallow water for a whole dive, the skills that you need to get right. On some trips (liveaboards etc) your guide or instructor might also insist that you complete a check dive before you go any further with the planned dives, this gives everyone a chance to have a practice and also for them to see if you need any additional support. Don't be worried by a request for a check dive, its perfectly normal and you should actually be pleased that you are being asked, imagine if there is someone in your group that hasn't done the preparation you have, and needs assistance with out being checked first!
Anything longer than 6 months out of the water and you would benefit from a refresher course or a skills review session. This will give you enough time to practice and make sure everything is in place ready for your next dive. Your confidence will improve in the knowledge that you have spent time on your own ability and are ready to dive once again.
So what should you do? Practice until you cant do it wrong, keep a log book and be prepared to invest some time in your own ability. You will enjoy your diving much more and feel the benefit of a more relaxed experience.