Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.

Sentence1: Marine dolphins are endangered by fishing nets, speedboats, and pollution. 
Sentence2: dolphins live mainly in shallow coastal waters.
dolphins

Sentence1: Caverns Secrets are hidden in caves. 
Sentence2: hidden caves are formed by carbonic acid in groundwater seeping through rock and dissolving limestone.
are

Sentence1: looking at bright objects has a negative impact on the eyes. 
Sentence2: Looking at bright objects have a negative impact on the retina.

bright