What type of sentence is this?When I go swimming, I have to keep my eyes closed underwater.

Explanation

This sentence is an example of complex sentence.It has an independent clause (main clause): "I have to keep my eyes closed underwater" and a dependent clause (subordinate clause): "When I go swimming".The dependent clause "When I go swimming" cannot stand alone as a complete sentence, and it relies on the main clause to make sense. The word "when" is a subordinating conjunction that introduces the dependent clause and indicates the condition or circumstance under which the main action takes place.