Which technique should lifeguards prioritize for rescuing a swimmer refusing help?

When a lifeguard encounters a swimmer who is refusing help, the most effective technique is to use a flotation device combined with verbal reassurance. This approach respects the swimmer's autonomy while still ensuring their safety. The flotation device provides immediate buoyancy and support, which is crucial if the swimmer is in distress. Meanwhile, verbal reassurance helps calm the swimmer and encourages them to accept assistance. Effective communication can often help alleviate fear or panic, making it more likely for the swimmer to cooperate.

Employing physical restraint or forceful methods, as suggested in other options, could lead to increased anxiety and potentially exacerbate the situation, putting both the swimmer and the rescuer at risk. Ignoring the swimmer entirely leaves them vulnerable, and tackling them could create an additional hazard, both in terms of physical safety and trust. The balance of providing reassurance while ensuring the swimmer’s physical safety is key to a successful and safe rescue operation.