Floatation depends upon the density. If an object has density less than the density of water, it floats. Principle of floatation is stated by the Archimedes principles
Archimedes’ Principle states that the force exerted on an object in a fluid is equal to the weight of fluid displaced (moved out of the way) by the object. This force is called buoyant force. The buoyant force pushes upwards against the object. Gravity exerts a downward force on the object (its weight), which is determined by the object’s mass. So if the force exerted downward on the object by gravity is less than the buoyant force, the object will float. vice vesa
If an object has a density less than the density of water, it floats and if the density of the object is greater that of water its sinks This causes the ship to displace water with a weight equal to the weight of the ship. On the other hand, the needle displaces more water than its weight and hence it sinks