Temperature
The deeper inside a cave you go the colder it is going to get. Temperatures can reach extreme lows that could easily induce hypothermia. Any water that you encounter is going to be extremely cold and ice is not uncommon deep within a cave. A fleece suit, polypropylene underwear, and waterproof clothing are essential in these temperatures. If diving you will need a wetsuit in order to withstand the cold water. Dry, warm caves do exist, so thin clothing may be suitable at times.
Safety
Caving can be an extremely dangerous sport and many die every year. Flash flooding that can completely fill a cave is one of the most dangerous aspects to caving and kills the most amounts of spelunkers. You should know the weather before you enter the cave and consult with experts as to how often flooding occurs. Other dangers include getting hypothermia from the cold, getting hit by falling rocks, and collapses, although this is more common in mines. There are a few things you can do to make your caving experience safer. Make sure people outside the cave know you are inside. Wear helmets to protect your head. Wear warm clothing. Make sure you have sufficient lighting including back up. You should take every precaution necessary as rescue operations are difficult, time consuming, and rarely work out for the best. Rescuers need special skills, training, and equipment and need to race against a ticking clock. Rescue operations often put the rescuers in just as much danger as the victims.
National Parks/Restricted Access
Many nations have protected caves or have made them a part of nature or geological reserves. You will need permission to enter the restricted caves. Fines are extremely high in most cases. Usually the areas are well marked, but you should check out a local map anyway to be sure. Speleologists, scientists who study caves, are sometimes the only ones who can make the decision on whether or not to allow public access and even they may limit their activity in a particular cave.
Cave Conservation
Access to many caves are restricted because the environments inside are extremely fragile and many of the creatures inside are rare. Speleothems can be damaged by light touches and passageways can be ruined by an inexperienced caver. Many caves hold significant amounts of water which are then sent out through streams and waterways, if polluted they may contaminate someone’s drinking water.
Creepy Crawlies
Many worst nightmares are about the things we find in caves. The underground passageways are home to everything form bats, snakes, spiders, rats, slugs, ants, centipedes, lizards, and everything else that loves the dark, has glowing eyes, and scurries. For women and men with long hair be sure to tie it up or tuck it in. You can buy masks if these creatures touching your face, although extremely rare, is a major concern. Killing these creatures is also a big no-no, as many are considered rare and within the boundaries of national parks.