Is it okay to take a 9 month old swimming in a lake?
Eh... you don't know what's in the water, so I wouldn't trust it.
I say go for it.
I wouldnt do it as an adult
It depends on what kind of lake I took DD into the spring but that is a spring. The water is freshly filtered and crystal clear
I've taken my 9 month old swimming in a lake twice...she didn't die or contract some strange disease. It was fine.