Yes, this sentence is a compound sentence. A compound sentence is a sentence that has two or more nouns or/and predicates joined with commas, semicolons, or conjunctions. In this is sentence, but is the conjunction. They is a predicate and sea and shore are nouns. Also you can break this sentence into two sentences: They spend most of their lives at sea. They come out to shore for one purpose- to lay eggs.
Thanks to a project called After Dark which uses robots to broadcast gallery tours via a web feed, people from around the world <em>have </em>the opportunity to visit London's Tate Britain art gallery from the comfort of their homes.
