Swim spas vary greatly in size and choosing the right size is a matter of available space and your primary reason for choosing a swim spa. Of course, your garden will dictate the maximum size you can realistically fill with a swim spa but also consider access and positioning. Small swim spas tend to have less seating area and are therefore only really suitable for 1-2 people at a time and stronger swimmers may need to use a swim harness to avoid forward and backward drift.
The stronger swimmer you are then the larger swim spa you will likely want in order to swim freely. A larger swim spa will allow for stronger jets whilst keeping water turbulence to a minimum. For big gatherings look for large swim spas with a good array of jets and seating. Bench seats around the perimeter are particularly good for party houses! Cal swim spas start from 3.60m in length and go up to 5.35m in length for Dual Zone models