There are not too many things that are going to hurt you in coastal waters. You are more likely to suffer from sunburn or a coconut falling on you than by assault by any marine beasty. But here are a few things to be aware of.
Sunburn – the tropical sun is really really strong, especially from about noon till 4pm. Just because you’re cool in the water doesn’t mean you aren’t being sunburned to a cinder. Wear waterproof sun cream and a t-shirt and long shorts and a hat (yes, a hat) while you are snorkelling for at least the first week after you arrive. You can also get sunburn on your face-down side. Wear waterproof suncream on your face. If you are going to be snorkelling for a long time, take a little shampoo bottle of it with you (in a zip pocket) for re-application.
Theft – don’t leave your valuables on the beach. Leave them in a safe place at your accommodation. At a stretch, arrange to leave low-ish value items with beach vendors. Keys and cash are generally waterproof, you can always take them with you into the sea.
Coconuts – a 3kg coconut falling from a 10 metre tree will make a real nasty mess of your head. Coconut killings are the single highest cause of holiday deaths in Asia. Don’t sit underneath coconut trees!
Lacerated soles – you might have to walk into the water over sharp stones or fragments of dead coral. If the tide is going out, what was an easy, sandy entry into the water, might not be so easy coming out. I wear a pair of scuba divers’ neoprene booties. You can walk around in them on land, too. Or you can take some normal rubber flip-flops in with you and when you are fully floated, tie them on to your swimming costume with a bit of string you have brought along. If you’re wearing slip-on fins, you’re supposed to do any walking in a backwards direction. Generally, it’s better to get horizontal in the water as soon as possible, rather than staggering around on your feet until you are waist deep. See also stonefish and sea urchins.
Sea snakes – the black and silver banded sea snake is pretty venomous. It is also pretty chilled out and will happily swim around sniffing under rocks with you right behind it, following its every move. It will ignore you. The only time to be concerned is if you get between the snake and the surface when it is coming up to breathe, in which case, get out of the way.
Cone shells – ahhh, look at the pretty seashell. Thwuk, thud. Some conical seashells have a sharp barbed hook that shoots out and injects you with a deadly poison if you disturb it. Don’t pick up conical seashells from underwater. Here’s a link to more information, including pictures of what they look like.
Stonefish/Scorpionfish – these well camouflaged dudes just sit on the bottom of the sea, secure in the knowledge that they don’t need to swim away from any splashing or disturbance, because they have extremely venomous spines on their backs. Stepping on one will do you a LOT of damage. Fortunately they are reasonably rare. The only thing to do to avoid them is to get horizontal in the water as early as possible, so you are swimming and not walking. Wearing something solid on your feet is the next-best options.
Currents – people getting swept out to sea is quite a common cause of fatalities. Just use your common sense and swim within your limits. Wearing something fluorescent is a good idea. See Tezza’s advice on rip-currents. Also see this separate page for snorkelling expeditions using kayaks.
Boats – Don’t rely on boat drivers not to run you over. Modern outboard motors that the yachties use on their tenders make almost no noise at all, so you might not hear them coming. Sometimes the guy paid to drive the speedboat ferry/banana-ride boat is more interested in racing with his buddy than looking out for turtles or snorkellers in front of him. A fluorescent tip to your snorkel increases your visibility quite a bit; wearing a bright or fluorescent swim cap might also help. Consider taking a surface marker buoy with you. But once a speedboat has picked up speed and the bow has gone up in the air, the driver probably can’t see what’s ahead of him whatever you are wearing. If you get stuck in an impending-doom scenario, try the power of shouting. As a last resort, dive down and stay underwater until the boat has passed. Try to check whether there is another one behind first, tho’.
Jellyfish – only a few species of jellyfish are deadly poisonous and, AFAIK, these all live in Australia. Generally, the worst you will get in the coastal waters of Asia is like a bee/wasp sting that will sting like hell for the first 2 seconds, then itch for about a week afterwards. It’s better to stay away from those jellyfish with trailing tentacles. Smaller, translucent stingies (without tentacles) will typically give you a rash and itch for a few days. Vinegar and urine are supposed to relieve the pain, but prevention is better than cure and a long sleeved t-shirt will keep most things at bay. In Thailand, they have put up stations with a bottle of vinegar for treating stings and a poster showing the worst types of jellyfish, (including box jellyfish).
Here’s a picture of the jellyfish on the poster. The rest of it reads:
Q: If I am stung, what will happen? / A: Various symptoms can be found ranging from minor irritation, such as itching and slight rashes, to major health problems, such as heart and respiratory failure, depending on each person’s resistance. / Q: So how should I deal with the stings ? / A: Do not attempt to rub or scratch over the stung area. Instead, pour normal household vinegar (concentration of 4-6x) over it for 30 seconds, like in the picture. You can also soak a small injured part of body (e.g.fingers) in vinegar. The vinegar is in this cylinder, right here.
. . Happliy, so far, I haven’t seen any of the poster’s stars.
Coral stings/burns – Many types of hard coral will give you burns as well as abrasions for a few days if you touch them, even if you just brush against them. Touching coral is bad for the coral and bad for you. Just don’t do it.
Sea urchins – are spiny little balls that sit at the bottom of the sea and have sharp spines sticking out in all directions. In some species the spines are coated with a poisonous mucus. These are another stepping hazard. If you step on one, the spines will break off inside your skin and the fragments are almost impossible to remove. If you get one, don’t leave it in there, get it taken out.
Sharks – sharks ain’t gonna get close enough to you to hurt you. See this separate article – “scared about sharks ?”. If you sustain a cut and are bleeding in the water, it would be prudent to get out.
Moray Eels – Moray eels hide in holes under rocks. They have sharp teeth and look mean in pictures. Some species can be pretty big, upto a couple of metres long. But don’t worry, Moray eels are wimps. They will retreat into their holes as soon as they see anyone bigger than them approaching. They would only bite you if you stick your hand right into their holes. So don’t go sticking your hand into dark holes.
Sting Rays – Sting rays have a barb with a venomous spine at the base (not the tip) of their tails. They live on the sandy bottom eating the tasty morsels living under the sand. In theory, you could step on one and get stung, but in reality they are scardey-cats and are very sensitive to motion. They will have swam away long before you even get close. Unless you try hugging a 2 metre one, you will be fine.
Needlefish. Needlefish are skinny silver fish about 40cm long that swim near the surface and often follow you around when you are snorkelling. They have lots of tiny (needle-like) teeth, which can look a bit scary in close up pictures. But needlefish are wimps, too. They won’t come any closer to you than about 2 metres. People sometimes get them confused with Barracuda.
Barracuda. You will rarely see a barracuda while snorkelling. They look like double-sized needlefish and have a mean look on their face and lots of teeth. However, they are pretty elusive and if you do see one it is unlikely to come closer than about 2 metres. They are said to attach shiny things like earrings or glinty watches which they mistake for small fish, but I have seen plenty of them while Diving (with an airtank) and they have all seemed pretty damned timid to me.
Triggerfish. When Titan Triggerfish are nesting they can become territorial and aggressive. Normally, they are scardey-cats and will stay away from you, but nesting one will rush at you repeatedly, trying to take a bite. Their teeth aren’t sharp but they have extremely strong jaws and could do some damage to an unprotected toe. If one comes at you, try kicking it in the face with your heel just as it reaches you. If you are facing it, a side-swipe punch to the side of the head might divert it for a bit. Then get out of its territory – it won’t stop coming at you until you are clear of its patch. 99% of the time they are perfectly docile.
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Anyway, sorry if I scared you. As you can see, most sea creatures are more frightened of you than you are of them. If you have a mask, some eyes and a brain, you will be fine.