Safety in Langkawi
Speedboats can often bounce off the waves at very high speeds and passengers can get quite strong jolts into the non-sprung seats, so persons with back or neck problems should not travel on the speedboats, but on the ferry. There have been reports of serious back injuries happening on the speedboats. They are also known as 'vomit comets' due to the number of people succumbing to sea sickness. Bring lots of water and be prepared for a bumpy ride!
Be careful driving around Langkawi at night. Although main roads are well-lit, some of the more minor roads are not very well lit and may pass through Kampungs (traditional Malay villages) or rural areas where the locals seem to take a very casual approach to road safety. Drive slow and watch out for erratically piloted motorbikes, pedestrians and livestock. Inside Kuah Town, watch out for errors in the road arrows - they may lead you into wrong lanes or into barricades. at night, watch out for water buffalo sleeping in the road.
Crime is generally not a problem on Langkawi, especially compared to the larger cities in Malaysia. In theory, you don't even have to lock your car, because it cannot get off the island without customs knowing about it!
Beware of smart wild monkeys. Those at Tengkorak beach attack humans who have food. If attacked, pick up stones (or just pretend to do so) and throw them at the monkeys, this will scare them away. Also, do not carry plastic bags as the monkeys associate these with food. Don't let them get too close to you or they will steal your (sun)glasses.
The biggest health risk on Langkawi is from jellyfish stings, especially during January - June season. Uninformed visitors are stung every day and the lifeguards on Pantai Cenang and the hospital treat more or less severe cases of jellyfish stings most days. There are several species of jellyfish in Langkawi's waters, while most will give you a nasty sting or a burn, there are some that will cause partial paralysis or even kill, in case of the lethal box jellyfish. If you have been stung badly, don't exert yourself physically as this will pump the toxins around the bloodstream and aggravate the symptoms. Vinegar is the only scientifically proven treatment for tropical jellyfish stings, apply it for 30 seconds to block toxin which has not yet been absorbed into the blood. To stay safe, swim only in stinger suit.
Langkawi can have a lot of mosquitoes depending on the time of year and location (i.e. Mangrove areas), so don't forget to use mosquito repellent. "Off" spray and various citronella or DEET based products are available in most supermarkets.
Average temperatures are hot or hotter; it's the tropics. Be sure to stay hydrated. You will need to drink about 3 litres a day and don't wait till you are thirsty to drink. Room temperature water preferably. De-hydration accounts for a large percentage of dodgy tummy holiday illnesses.