What do you mean, "the sea turns tofu boat: go in the water, go in the water"?

Tofu is made of soybean milk and brine, so we say "come in the water". When the tofu boat capsizes in the sea, the tofu will sink into the sea and disappear, so we say "go into the water".

This two-part allegorical saying means, where it comes from, it is used in the same place; How to get it and how to use it in the same way.