Actual lake balls can be a risk as there is no knowing how long they have been submerged. But you can buy "found" balls, ones that have supposedly not been dunked!
A couple of weeks underwater will probably have little effect, a couple of months probably a bit more.
To all those who shy away from lake/found balls I ask this...
If you find a seemingly new ProV1 in the rough, are you going to use it? If so how do you know its not a lake ball that has been submerged for months before being cleaned..?
I'm not convinced that most lake balls differ significantly from new ones once the new ones have been hit a few times.......
Refuge, though, are a different kettle of fish!
And the concept that balls degrade noticeably when submerged for even quite long periods is a myth too!
Not according to the guys at Titleist when asked the question