这个聊天群里有很多潜水员，他们只看消息从不发言。

There are many ___lurkers in this group chat who only read messages but never reply.

警察在巷子里发现了一个潜伏者，他正躲在阴影中窥视。

The police found a ___lurker in the alley, hiding in the shadows and watching.