Area dependant, common for fire service water rescue units to also be at small stations. Some small stations also have a combined water/cliff rescue resource such as a 4x4 or van and boat trailer.
That's why I specified for SFRS, almost every station with Water Rescue here is fairly large or at least above average. If you read above you will also see I understand in some other regions within the UK it works differently and that because of that it's not really my place to talk.