How do ships float.....?

simply put: the hull of the ship pushes down on the surface of the water with a force equal to the weight of the ship. the surface of the water pushes up on the hull with a force equal to the weight of the water that is displaced (displaced = pushed out of the way). when the ship is set down into the ocean, it sinks until it has displaced an amount of water that weighs as much as the ship, and that's the depth at which it floats. fresh water weighs around 67 lbs per cubic foot, sea water weighs a little bit more.

The shape of the boat helps the boat displace water which has to be a greater than the ships weight.

Buoyancy over displacement! A vessel of any size or shape displaces water. Steel or concrete, etc. weighs more than water and will sink. The trick is to keep all exposed openings for water to enter "above waterline". Shape of vessel only allows utilization for certain usage. It does not matter as far as being able to float is concerned. Design criteria is developed around intended usage to make the vessel seaworthy are structural suitable for purpose intended. Oceangoing vessels as compared to dry docks etc. Vessels under powered propulsion must be designed to accommodate that usage. High speed pleasure boats are designed differently than ocean going bulk carriers. If you really want to peak your curiosity; visit a submarine some day. They will blow your mind regarding ability to float!

Any object floats when the weight of the water displaced by the object weighs more than the object. That is why as a ship is loaded it sinks lower into the water so more weight is displaced.