that is because the walls of the plate are keeping the water from coming in the plate. How ever if you drop a plate down in the water hard, it is going to sink. Put it gently in the water
There are tents designed to Float in water. But not all tents designed to float.
Soil floats on water!
When cleaning acrylic Plexiglass it is very important to use a clean soft terry cloth towel or cheese cloth. Do not use paper towels. Paper towel fibers are to coarse and will scratch the surface of the Plexiglass. Paper towels will also leave streaks on the surface of the Plexiglass which will restrict visibility. Microfiber cloths are also terrific to use if you have them handy. Plexiglass has a very soft surface which can easily be scratched. When cleaning Plexiglass, always make sure that you are using a soft, clean cloth. First, blow the dust or dirt off, or use water and a soft cloth to float the dirt off. Then use a recommended cleaner to complete the job. Note: a mild solution of dish detergent and warm water takes off stubborn dirt easily without harming the acrylic Sort of float the dirt off. Please... never, ever, use cleaners containing ammonia. Cleaners such as Windex or 409 will harm your piece of acrylic. Use only products specifically recommended for cleaning acrylic such as Novus #1, Plexiclear or Brillianize etc.
As heptane is lighter than water, it will float.
Objects that float in water have a lower density than water. -anonymous18_K