Canine hydrotherapy in the UK is typically delivered in a swimming pool or using an underwater treadmill; hydrotherapy for rehabilitation should centre on encouraging correct limb movement within the water, regardless of the modality in which it is delivered. Veterinary consent is required before starting hydrotherapy, which enables the hydrotherapist to understand the dog’s condition. The properties of water are harnessed to enable safe and comfortable exercise, and a good understanding of these properties is needed for the design and implementation of a specific programme tailored to meet the needs of an individual dog. Hydrotherapy has a role in the treatment plan for a range of conditions, including obesity, pre-operative muscle conditioning, the conservative management of developmental orthopaedic diseases, such as hip dysplasia, and post-operative recovery from orthopaedic surgery; it can also be used palliatively, for fitness and for emotional wellbeing. Contraindications include unhealed surgical incisions, skin infection, emesis and diarrhoea. Two case studies demonstrate different areas in which hydrotherapy can help dogs. The aim of this article is to increase awareness of the benefits of hydrotherapy among veterinary professionals.