Lots of boat builders and designers will use models in a variety of ways. Interior layout is probably the most common, or even just getting an idea of the shape and look of a craft before building in full scale.
Often somebody will decide to build a model and see how it performs. Be careful here. There are lots of issues when scaling something down and then expecting it to perform in a non-scaled physical world. The dynamics of water don’t change just because the hull got smaller. The strength of materials is not linear, nor is the weight.
There are lots of ways to use models to learn about full size performance (its been done for centuries), but there are lots of considerations. The study of this type of interaction is the basis of this "similitude" topic. Check it out for some interesting info.