Sinkholes in above ground pool

[soupydude]

I got hit with voles(similar to moles) this season which left a 3 foot long trench at the bottom of my 1 year old liner.
I'm looking for advice if there's a way to repair the trench without draining the pool. The trench is 3 ft long by 8 inches wide and about 3 inches deep. I'm going to try a toilet plunger to see if that works but I could use some suggestions.

 

[Bama Rambler]

Other than draining the pool and filling the voids I don't think you're going to have much luck. I wish it was better news.