If they sink for me before they show some leg, I always pour out some of the water so they're closer to O2 which they need as much as moisture. Some growers swear by hydrogen peroxide which serves two purposes. It adds oxygen to the water and helps kill off pathogens.
I only let them swim for about 48 hours if they haven't broken out before then. If they have, I plant them as soon as I see the white root which I plant facing down about 1/4" beneath the soil surface.
If they don't, I put them between sheets of paper towels in a half open plastic baggie to help keep the paper towels from drying out, but also giving access to oxygen, and then into a dark, warm place.