Sometimes bags tend to float horizontally instead of being submerged in a vertical position. This may especially be the case with Ziploc-bags with some minimal residual air, or with very fatty food.
Most often, suspending the bags on a skewer will do the job. In addition, marbles or glass beads may be placed in the bottom of the bag.
--PedroG 01:00, March 15, 2010 (UTC)