What does a water passenger mean?

Nowadays, water passengers are not the simple concepts of boatmen and fishermen. Nowadays, water passengers mainly refer to people who often travel between the mainland, Hong Kong and Macao, taking products in and out. They brought at least a few cans of milk powder, most of which were smuggled by boat, worth hundreds of millions of yuan. As we all know, Hong Kong and Macao have low tariffs and electronic products are cheaper than those in the Mainland, so there are professional water passengers. They go back and forth once or twice a day, maybe a dozen times. They come from Hong Kong and Macao and carry different electronic products with them, such as mobile phones and computers, and sell them in the Mainland, or help others earn the difference or wages. On the contrary, Chinese mainland's food, seafood and specialty products are cheaper, and water customers can also take these products from Chinese mainland to Hong Kong and Macao to sell, or help others bring them to earn the difference or wages. The most typical case of water passengers carrying cargo occurred in the melamine period. At that time, most of the domestic milk powder was inferior, and some water passengers brought milk powder imported from Hong Kong and Macao into the mainland to earn the difference. They can bring seven or eight plastic cans at a time, and the profit is considerable.