“Free-form” pool provides a more relaxed and natural look. This look is usually accomplished with some combination of the following:
Gentle curves, non-traditional shapes
Natural rock, flagstone or “rolled beams” around the perimeter
Natural rock or stone built-in at various places around the pool
Rock or stone pavers, exposed aggregate, scrolled or stamped concrete
Use a combination of these features, and you can get the feel of a natural oasis. Combine some of these features with features of a classic / formal pool, and you can “class up” the look as much as you want.