User blog comment:Plexioth- xD/Monster Hunter 3 Ultimate/@comment-76.69.5.128-20111024011801/@comment-1758220-20111024143225

The thing with mountain stream is that any water there is either way too shallow or a fast-moving rapid. The only place I could see underwater exploration is the large lake off of area 7. Come to think of it, that would actually have been pretty cool.