Some lakes (many lakes) are not mapped well - particularly up north in SK and MB. BUT the resorts can usually outline areas where you need to be careful. In terms of having some sort of sonar "looking ahead" these are typically deployed on your bow mount trolling motor or on a dedicated pole mount - and in both cases the speed is limited to a few kms/hr.
There isn't anything I'm aware of that will allow you bomb down a lake at 60km/hr and get an accurate (and reliable) picture far enough in front of you so you can react and avoid running into a shallow reef.
Best thing is to get some local knowledge and a map and slow down through (and self map) areas you have travelled. Live Maps are available now on every brand of unit. Once you have been over an area, you know that line is safe.
foreward sonar
Linear Mode
