a mimetic word for things swarming or crawling in large numbers; used when insects, small animals, etc., or crowds are teeming.
浜辺にはクラゲがうようよいて、泳げなかった。
The beach was crawling with jellyfish, so I couldn't swim.
床の隙間に小さな虫がうようよしている。
Tiny insects are crawling in the cracks of the floor.
市場は朝から人がうようよして賑やかだ。
The market is bustling, full of people from the morning.