Question

A ship needs _ water so that the bottom do not touch the sea floor​

Answer 1

The answer really depends on:

whether you are talking about nuclear submarines or conventionally powered submarines; and
whether the submarine and its systems are designed to sit on the sea bed (particularly the hull and seawater interfaces).
If you have a conventionally powered submarine that is designed to be capable of ‘bottoming’, then the main questions are - what sea bed types, for how long and at what maximum and minimum depths?

Answer 2

Answer:

more density

sea water>ship