【推荐2】Why do people travel? Well, we usually travel because we want to see other countries and visit places that are famous, interesting or beautiful. We travel to meet new friends, to try new kinds of food, to experience life in other parts of the world or simply to get away from cold weather. However, there are other reasons for adventure travel. Many of today’s adventure travelers are looking for an unusual experience and adventure travel is becoming more and more popular. Here is a quick look at two popular activities: hiking and rafting.

Instead of spending your vacation on a bus, in a hotel or sitting on the beach, you may want to try hiking. Hiking is a great way to travel. You will get close to nature and take exercise at the same time. Hiking is easy to do and doesn’t have to be very expensive. You can hike close to home or other places. The basic equipment you need for hiking is simple: good shoes, clothes and a backpack. You can hike in the mountains, in a forest or along a river. You can also go for a hiking in the city.

Another exciting adventure is rafting. A raft is a small boat that you can use to paddle(划桨) down rivers and streams. Rafting is a good way to experience nature. If you want a normal rafting trip, choose a quiet stream or river that is wide and has few fallen trees or rocks. As with hiking, you should always think about your safety and wear good clothes. You also need to learn the basic skills, such as how to handle the raft, how to paddle and how to get in and out of the raft. You should not raft unless you know how to swim, and you should always wear a life jacket.

【推荐3】Camping often sounds like a great deal of fun: however, it does require some special preparation. Before going camping for the first time, make sure you have done some research on tents, food and wildlife survival.     1    

Make sure you pack the appropriate clothing for your trip. Check the weather forecast and bring the clothing that will be needed on your trip.     2     Remember to also pack a rain poncho （雨披）no matter what the weather forecast predicts.

Do not hesitate to pack too much for your kids. Being out in the wild can result in all sorts of messes. Kids are always attracted to dirt.     3     You can not really prevent it from happening, but you can pack extra clothes. Remember, always be prepared!

    4     Always choose one suitable for a temperature range just below what you're expecting, even in the summertime. Also, pay attention to the different materials used for sleeping bags. Sleeping bags made with synthetic（合成的）fibers will dry out faster if it rains unexpectedly, but natural fiber sleeping bags will be lighter to carry.

Make sure that you avoid any poisonous plants. A good way to do this is to stop at the ranger station （护林站）and ask what kinds of poisonous plants are in the area.     5    Never eat anything while hiking on the path if you do not know it is edible (可食用的).

【推荐3】Underwater travel is difficult and dangerous, but many people have reasons to stay deep under the ocean. Soldiers in submarines travel long distances underwater. Companies looking for oil and other resources stay underwater, too. Humans have come up with a few designs of vehicles to move around under the ocean. But what if there was a better way to travel?

Hilary Bart-Smith, an engineer at the University of Virginia, thinks a vehicle that travels like a man ta ray would be able to operate for long periods at sea as if it were a living organism. Manta rays, a type of cartilaginous (软骨的) fish, can grow up to 29 feet long, which are found throughout the world in tropical, subtropical, and temperate waters. Manta rays are some of the most efficient swimmers in the ocean. Different from animals and people pushing against water in order to swim, the manta ray swims by moving through the water with wing-like movements of their fins (鳍). Efficiency means using less energy to move farther and causing less pollution.

Bart-Smith and other engineers at the University of Virginia had to find out what manta rays looked like on the inside to better understand how they move. They took x-rays to find out how a manta ray’s fins are built. They found that a web of cartilage, which is the same kind of material that your ears and nose are made from, stretches across each fin.

Once the engineers knew how a manta ray’s fin was constructed, they could build one of their own. They made a long row of metal struts with many hinges to imitate the manta ray’s web of cartilage, acting like your finger, which can bend as one long line, or bend in many places to make a curve. The engineers put their design inside a flexible cover, shaped like a manta ray’s fin. Then they tested it in the university swimming pool. They were happy to see that it swam just like a manta ray in the ocean.

Engineers and scientists are still learning and experimenting with how to imitate these amazing animals. Perhaps someday engineers will be able to build manta ray robots that are big enough to transport people. For now, engineers study their movement and learn from the most efficient swimmers in the ocean.