English 
Is there any noise in the waterbed?
No, when the water mattress is first filled with water, the water in the mattress will come with air. Once the air is removed through the deflation tube, the water bed becomes silent.
Will I feel seasick on the water bed?
Not at all. Unless you move, the waterbed will not move. Anything you do on the waterbed will be light and will stop as soon as you stop. If you choose a very stable mattress, the movement of the bed will be reduced to the minimum support at any time. This will not minimize the need to turn over when you sleep.
I am heavier than the person I sleep with. Will we be comfortable on the same bed?
Will do. The water bed has the same support for you. If you are extraordinarily heavy, just choose the largest size water bed that your bedroom can accommodate and a full water mattress, you will find how comfortable it is. From a physics point of view, the more you sink, the more water is drained, and the water needed for the water bed is reduced.
Is it comfortable to sit on the water bed?
Yes, actually, it is. Sitting on the water bed is very comfortable. It would be better if you placed a round pad for your back at the same time. This way you have the most comfortable bed to read, write and watch TV.