Answer:
The river is very clean.
Explanation:
It indicates that the river is very clean since if you have fish and other invertebrates, you have to have some algae and water plants. If the river is dirty, little plants will grow and there won't be many fish and other invertebrates.
Johnny is always "out in the open", along with the rest of the outsiders. This may resemble how easy it is for the boys to get hurt, as they do not have any protection and are an easy target.