IPA: /ˌfluːviˈaɪtaɪl/
KK: /fluˈvaɪəˌtaɪl/
Relating to or found in rivers.
The fluviatile environment supports a diverse range of aquatic life.
Fluviatile is formed from "fluvius" (meaning river) and the suffix "-atile" (meaning pertaining to). The word describes something that pertains to or is found in rivers.
Think of 'fluvius' as relating to rivers, and remember that 'fluviatile' means something that is associated with or found in rivers.