Would like to know if its possible to scan for rare fishing pools such as Royal Ripples and Blood in the water.

Unfortunately, this is something Blizzard tries really hard to not let addons do. The resource tracking nodes on the minimap are done using a completely separate system from the easily-accessed vignettes for rares and treasure -- last time I looked into it a few years ago, the only practical way to scan for them was to completely take over the minimap frame and move it around under the mouse cursor, tracking how you've offset it from the cursor to determine the location and watching for whether it tries to show a tooltip for a resource node at any given offset. This is pretty fragile, and also doesn't work well if someone is trying to play WoW normally at the same time -- you can only really get away with it in a dedicated farming addon, where the player can put up with weird on-screen stuff in the name of gathering.