Li Du loved the island and wanted to name it.
Snake Island was the most natural name, but he didn't like it. First of all, the name was too common. Secondly, snakes were too evil to make a good name for the island.
He was thinking that Sophie had come to take him to the reef to look for scallops and oysters. There would possibly be a large number of sea snakes, as there were many shellfish on the rocks around the island.
Some people may not have understood the relationship, but it was quite simple. Some shrimp and crab species liked to eat shellfish, while sea snakes didn't like them because they couldn't digest the shells.
However, they could digest shrimp and crabs, and they could attack the sea animals they met. Unlike humans, sea animals had no intelligence, and they didn't know that they should retreat from the sea snakes. Instead, they rushed up to attack.