Place it immediately after the swimmer's successful lap in your edit, then follow it with clapping to turn the compliment into applause, keeping the focus on the swimmer's achievement throughout the sequence.
关于此声音
This is a short French spoken line, lasting about six seconds, in which a voice offers the swimmer a calm, admiring compliment. It feels warm and gently playful, like praise from someone watching proudly from the poolside, and it works because the words are simple, direct and easy to understand even without knowing the wider scene.