Air accumulates in a waterbed mattress from when you fill it and as the water is heated, releasing oxygen. These air bubbles can make your waterbed mattress less comfortable, and create a sloshing sound as you move on the mattress. Keeping the water properly conditioned (waterbed conditioner can be purchased through your waterbed company or online) will help to reduce air bubbles, but when you hear that telltale sound of air bubbles, you should remove the air to keep your bed comfortable.
Remove bedding. Locate the nozzle you fill the bed with. On most waterbed mattresses, this nozzle will be depressed. Pull it out, but leave the cap on for now.
Find the air bubbles. If you have a translucent mattress, it should be easy to spot the air bubbles. If you cannot see the bubbles through the mattress, then you may be able to locate them by pressing down on the mattress in 1-foot increments and feeling for the air.
Once you have a good idea where the air bubbles are, you need to herd them toward the nozzle. You can do this with your hands, applying gentle pressure and pulling them toward the air nozzle. Or if your mattress is queen or king size, you can lay on the mattress and roll, again pushing the air bubbles toward the nozzle.
You should be able to feel a substantial amount of air around the nozzle. If you pull it up and away from the mattress without water suction, you've trapped the bubble. Otherwise, repeat Step 3 until this occurs.
Remove the outer cap (for most waterbeds it is a screw top) and put it to the side. Sitting on the side of the bed frame (not on the mattress itself) lift the inner cap and slowly let the air escape. When water comes to the top of the nozzle, recap it. Check for bubbles again. If they remain, repeat Step 3 to Step 5 until you remove all the air.
Add waterbed conditioner when you burp the bed. If you have children, employ them to roll along the bed to herd the air bubbles. It is fun for them, and useful for you.
Be careful when you uncap the waterbed mattress. Do not have any pressure on the bed, or the water that spurts out could make a big mess.