Why do you say yaks are boats on the plateau?

Yak is a unique animal in Qinghai-Tibet Plateau. It has thick and long hair, can lie in the snow to keep out the cold, is short and strong, can climb mountains and carry loads, and is good at handling. It is an important means of transportation on the plateau and an indispensable livestock for Tibetans.

Camel: A boat in the desert. The camel is hungry and thirsty. People can ride camels across the desert, so camels are known as "boats in the desert".