Water is one of the most difficult materials to render. It has transparency, but not simple transparency, it starts transparent and become less and less as light travles though it, until it can't anymore, and then the water has no transparency left. And it's reflective too, but not as a mirror, it only reflects at low angles of incidence, so this has to be computed too.

Depending on the Vue version you have, you can tweak some settings.

So let's see what is your version of Vue.