Question

how can you appreciate the technology of making ships those float on water using the material which sink in water

Answer 1

A ship is hallow object made up of iron and steel which contains lots of air in it. as air has very low density. Due to the presence of a lot of air in it, the average density of ship becomes less than the density of water .
Thus a ship made up of iron and steel floats on water because its average density is less than the water.
when a ship is placed in water it sinks to a certain level such that the weight of water displaced by its submerged portion is equal to whole weight of ship. since ship fulfills the condition of floatation, it floats on water.