what's interesting,though,is what happens with them that liv

这是有上下文的吧.
你把though提出来就清楚了
what's interesting is what happens with them that live in caves.
有意思的是住在洞穴里的他们发生了什么?
再问： 原文：
再答： though应该翻译为“然而” 这句话要分析清楚what happens with them 是整句的宾语。后面的that引导的是定语从句。定语从句修饰的是them。是指鱼。