The TCH between Neys and Red Rock is nice. I don't swim so can't comment on the water quality. I stayed at Rainbow Falls Provincial Park - because it was very cool last May I got a last minute site right on the water:
https://imgur.com/a/E3pK1ja
I wasn't a fan of the noise from the truck traffic, but I basically ran out of options as I'd stupidly driven 900km that day, a terrible decision if you want to enjoy the scenery.
Driving back across the same strip in late July, I enjoyed the Wawa to Sault Ste Marie scenery. It was early Saturday morning and with beautiful weather, the TCH was virtually deserted, empty beaches at Old Woman Bay/Pancake Bay etc. By contrast, in May this stretch was somewhat treacherous with heavy fog and rain. I'm surprised more cyclists - I counted about 30 on the TCH across Canada - aren't killed or injured.
After driving the incredibly boring Yellowhead Highway from Edmonton to Winnipeg, and the stupidly slow TCH to the Ontario border, I couldn't help but let out a whoop of joy seeing the rocks, curves and hills heading towards Kenora. Ontario felt interesting ha.
North of Thunder Bay to Dryden is a really dull stretch, then it gets curvy rocky and hilly until near the Manitoba border, then very flat and dull until west of Regina. (Fuel economy really suffered driving into a strong headwind in the Saskatchewan hills west of Regina to Lethbridge.) Bruce Mines to Massey, with Blind River the coolest, is nice because of the frequent small towns, Old Order Mennonites and farms. At Massey, I dropped down into Lee Valley to Espanola. Espanola to Port Severn is super boring.