Your dog will run through puddles but disappears when you open the bathroom door. The water may not be the whole problem. A slippery tub, a loud tap, being held still, or shampoo near the eyes can make bath time unpleasant even for a dog who likes swimming.
If your dog needs a bath for a skin condition or has severe mats, ask your veterinarian or a qualified groomer for advice rather than postponing needed care while you train. If a bath is optional, take the pressure off. A damp cloth may be enough for a small patch of dirt today.
Make the bathroom easier first
Put a secure non-slip mat in the bath. Check the water temperature yourself, and avoid spraying the face or ears. Let your dog visit the bathroom without a bath happening. Reward a voluntary step toward the tub, then let them leave. Later, reward stepping into the dry tub. If they won't approach, start farther away, don't lift them in and shut the door to finish the exercise.
Introduce the sound of the tap on another day, while your dog has the option to move away. Then try a little water on a paw. Each step can be its own short session. Stop if your dog stiffens, trembles, or tries to escape. Your dog may need more space or a different way of being washed.
When you do wash them, use a dog-appropriate product your veterinarian recommends for their skin and rinse well. Keep it brief and dry them in a way they can tolerate. If the dryer is frightening, a towel and a warm room may be kinder, depending on their coat and health needs. Aim for a bath they can handle, not a perfect salon result in one go.
Sources: Hill's Pet: Why Do Dogs Hate Baths?. Dogs Trust: How to handle your dog.