Poule pas mouillée
Unlike his older counterpart (extra), the young lad with the fancy trunks, after much hesitation (long enough to lose all sensation in his toes), opted not to go for a swim after all.
His mate called him chicken. The French expression is "poule mouillée" (wet hen). Which seems a tad ironic.
Lesson of the day: it is not the fanciness of the swimwear that makes the swimmer.