Waterbeds have come a long way from their fluid-filled sack days in the 70's. Now they are encased inside a sturdier mattress with additional padding and features like heat and vibration for added comfort. Still, there are some things you cannot and should not do on or with a waterbed.
Some people like to hand-stitch things in bed as a means of relaxing before going to sleep. While you could still do your sewing and stitching hobbies on a waterbed, you may want to avoid the risk of poking the bed with anything. A scissors would have to hit the mattress hard, so there is little chance of damage from the scissors. However, repeated deep pokes with needles could cause tiny holes to form, which would slowly leak and eventually cause the mattress to fail. Other particularly sharp objects should also be removed and out of reach of the waterbed (e.g., no hanging two-fisted Claymore swords over the head of the bed).
No Trampoline-Like Moves or Wrestling Moves
Modern waterbeds are very durable, more so than their predecessors. Still, you do have to remember that at the core of every waterbed mattress there is a large vinyl bag of water. Constant movement, like jumping or bouncing on it, especially from a two-hundred pound adult (or heavier) could cause the water bag inside to burst. Wrestling moves on the waterbed as well as aggressive cannon-balling could also cause the mattress to burst. Find some alternatives for these types of play and save yourself the expense of replacing your waterbed mattress.
Leave Frayed, Live Electrical Wires or Charging Cords on or Near the Bed
If you are like most people, you probably leave your charging cords for your laptop and mobile devices plugged in everywhere. While that does not really seem dangerous, the truth is that these are still considered "live" electrical feeds because you have one end plugged into an outlet and nothing attached to the other end. If the charging end were to end up wet somehow, the electricity in the cord as it is connected to the wall would have a way out of the outlet and travel to wherever the water takes it. If you leave several open-ended charging cords hanging out on your waterbed, or you leave frayed cords laying out there, it only takes a single leak from the bed to make a major mess.
For more information, talk to a professional like Waterbeds Today.