Source:
https://scmp.com/news/hong-kong/article/1052605/why-lamma-iv-sank-so-quickly Hong Kong
Why the Lamma IV sank so quickly
Flooding of compartments and possibly open doors would have caused rapid sinking of stern that left passengers so little time to escape
The Lamma IV which was partially sunk in the waters off Lamma Island is lifted up from the sea yesterday. Photo: Sam Tsang
Two watertight compartments at the rear of one of the vessels involved in the Lamma sea disaster probably ruptured and filled with water after it was hit by the other. This caused it to stand on its tail and sink quickly, a marine engineering expert said.