It might sound weird to have a pool or a jakuzzi as big as a pool on a yacht's deck. However it is so common and above a certain length; it is considered almost as a "must".
Well actually guests on board, spend most of their time around those pools. Check the photos below and you would understrand why...
Design is the Salt X Pepper of life. It is not a must, but if you have it, then you have the appetite for life.