Ice rods...freeze water in sections of PVC and push them out the end. Make enough to do the job ahead of time. Lay them out, roll across them and leave them in place. They will melt, safe will be on the floor, nothing to have to remove and the little bit of water left will evaporate and dry up.
Seems it would work fine...
Above is based on the opinion of a 20 year Small Arms Marksmanship and Training Unit USAF instructor with more than 30 years in competitive shooting sports. Your mileage may vary.