By the time Michael Chai spotted the other boat bearing down on his craft, it was too late to shout a warning to the captain.

The boats crashed into each other. Within seconds, he and 17 other Taiwanese tourists were plunged into Vietnam's famed Halong Bay, without life jackets, fighting to survive.

Five drowned in Wednesday's accident, leaving grieving families in Taiwan and questions over safety standards for one of Vietnam's most visited tourist attractions.

Chai says he loves Vietnam but the "government should be responsible for this."

Each day, up to 10,000 tourists from around the world sail Halong Bay. But at least four deadly accidents over the last 10 years and many more incidents recounted on travelers' blogs have led to allegations that tourist boats are cutting corners.