When a dog performs a fearful or aggressive behavior it’s as though they are saying, “I don’t have the skills to behave in any other way in this situation.” Why would you want to make them repeat themselves?
If you were to drop a kid into a pool that was just deep enough they didn’t feel completely safe you could expect them to try to get out. Some kids might find the exercise educational and learn to tread water, kick their feet, blow bubbles, or dog paddle. Others might continuously get themselves to the side and hang on. If the latter is good enough for you, then keep doing it, but it’s a step short of what would help them feel better about being in a pool and give them skills so that if they find themselves in any body of water they are less likely to drown.
Skill building is not only what the dog training business is all about (or should be!) it’s incredibly rewarding to see a dog develop the skills they need to find other ways to enjoy their life. Not being able to swim keeps many people from participating in activities that are healthy and fun. Not being comfortable in places where there are people or dogs puts limits on the opportunities to discover the joys of simply being alive.
If they need support and feel better hanging on to the side, that’s ok let them. But remember that the combination of counterconditioning and training using positive reinforcement can lead to the day that rather than trying to avoid the water they embrace their ability to float and start having fun in the pool. While they’re learning, their desire to keep heading for the ladder out is information that they need more counterconditioning and reinforcement for kicking their feet and practicing strokes.