You can find divers and places to dive in all corners of the globe. The world’s surface is pretty much 70% water with underground diving too inland on top of that so there’s never an excuse that there isn’t any diving nearby but there are some reasons not to go diving though. As awesome as scuba diving is you should never take it lightly and you can hurt yourself quite badly if something happens in the water.
When I was diving with a friend out in Egypt, the night before he decided to have a glass of the house red wine, which needless to say wasn’t the best. It did, however, stick with him all the way until we were out in the water the following day. Then it really wanted out… That being bad enough, he was also on a rebreather at the time, so when he needed to purge underwater it’s not as easy on a CCR as you have to close the loop and reopen it to take the mouthpiece out and put it back in. Otherwise, that wine just recirculates back to you in a few seconds and floods your scrubber, unlike a normal regulator.
Rental gear is made to be tough and cheap so the dive centre can afford a whole range but that doesn’t mean it lasts forever. I won’t mention the place but you have to use their regulators to dive there and these things get used by a new diver every hour, on the hour, every day so they’re pretty knackered faster than usual. The rubber hoses on the regs I had were flaking and it turns out that the exhaust valve was knackered too, that I only found out when I looked up, 30m down and my 2nd stage filled with water. Luckily my airway control is on point but the next diver may have choked… I also had a brand new rental drysuit up in Norway, great, until you put it on and the brand new latex neck seal tried to kill me. Most drysuit divers stretch their neck seals overnight at least, this one had no such treatment.
I’ll be the first to admit that I don't check my tyres or oil levels in my car before every journey but I will always check my own gear right before a dive because it is so easy to just throw everything on and jump in only to realise your air isn’t turned on so you only really have three breaths. Every part of your kit needs to be looked over before every dive from every O-Ring on your regulator to the fin strap on your fins. If an O-Ring fails during the dive, you’re going to have a bad day, if a fin strap breaks during the dive, you’re going to have a bad day. I used to avoid asking divers about their kit because I didn’t want to be "that guy" until the diver I was following had an O-ring blow on a swivel that 10 minutes before I almost asked when the last time he tightened it was. We both ascended fine and nobody was hurt but it all could have been avoided with one simple question and if something is going to go wrong, it’s going to go wrong at the worst time.
Everything about scuba diving is pushing your limits and boundaries, I mean you are literally going where humans are not made to go, but you need to know your limits. Going down too deep is probably the easiest but while we do teach you a lot during your Open Water course we often don’t teach you about partial pressures and other complexities about going deeper in detail. If you’re not paying attention you can drift down pretty far without noticing and the first thing that will happen is that you use your air much faster than you’re used to. Another problem can be that you can’t simply ascend straight to the surface so you’d better have enough air to get you there. Swimming into wrecks and caves without proper training is pretty dangerous too. It’s super easy to get turned around and no matter how good your sense of direction is, trust me, you’ll get lost if you’re not careful, we have dedicated procedures and equipment for navigating overhead environments safely but if your not qualified or haven’t been trained yet then there’s no shame in backing out.
There was a tv advert a while back with a guy deciding between two shark diving cages on holiday, the expensive one that looked the part, or the cheap ropey looking cage that was falling apart. The joke was that he went with a sketchy cage because it was cheaper but you’ll still find sketchy dive centres around the world that are best left alone. If they can’t organise their paperwork or equipment or they give you gear that "well, hey that’ll do" then just get out of there. If they can’t organise paperwork or properly fitting gear then would you trust them to get you out of a tight spot and to a chamber efficiently?
Computer algorithms don’t take illness into account and there is plenty of research that has found that the more worn down you are, the less efficient your decompression is so while your dive computer may think and say that everything is fine you can be well beyond the line and actually hurt yourself. Medications may make you feel better but I’ll bet you anything pretty few of them have been tested under pressure so the pharmaceutical companies have no idea how the drugs will act at any depth. Medications also wear off so it’s best to just avoid the situation completely. Congestion is one of the worst, if you have the sniffles then that mucus filling your sinuses and air spaces in your head will shift around during the dive and create nasty air pockets that trap air as you ascend, that's a reverse block your dive Instructor warned you about.
Never dive alone, that’s one of the golden rules that should have been drilled into your head from your 1st day. Even those with a Solo Diver certification will still dive in a pair or a team because every other diver in the water with you is an extra air source and pair of hands to get you out of trouble. The internet is full of horrible stories of divers cleaning their pools or the underside of their boat by themselves and getting stuck only to be found too late and the worst has happened. Diving in a three is a similar way to get separated if you thought losing your one and only buddy is easy then trust me, losing both buddies when diving in a three is far easier. As they swim off together they’ll look around see one of their buddies and continue with the dive leaving you to fend for yourself wherever you stopped to take a picture.
If you’re not 100% happy with the conditions, the dive plan or anything then there is no shame in not jumping in and if anybody gives you any grief tell them to get over themselves. Jumping in when you’re unsure about something actually makes you a liability in the water, not only risking your wellbeing but others too. Every person in the water acts as a backup for everybody else so if one link in the chain isn’t working properly then any strain will break it. It’s always better to dive another day if you’re not feeling happy about everything.