I don't know if this is a multiple choice question or not, but the word pleasant is very vague and imprecise - much like the word interesting, even though this doesn't appear in the text. Since the writer is talking about an academic, although surely equally fun, experience, and since he or she has included more specific and technical words, such as nocturnal sea animals and squirrelfish, the word pleasant does not seem very concrete or descriptive. He or she could have used other words such as fascinating, enriching or eye-opening.
