蛟龙得水

jiāolóng-déshuǐ

[to have an opportunity to bring one's ability into full play] 蛟龙欣逢雨水。 喻指君主得民心; 英雄逢时大有凭藉、 施展之机

所谓蛟龙得水之秋, 自此一举, 此后不复与诸君伍矣。 --《北史》