The purpose of the sentence is to make memories for the college as a remembrance for future endeavours to come by.
Step-by-step explanation:
The option for the question has not been stated, hence in general, it might be the best possible purpose to be made out of the sentence, to make memories as a remembrance for the college.
The future endeavours as such as college is supposed to distant the best friends as they might be going to different colleges, thereby, to acknowledge this upcoming phase, the one last summer adventure is chosen.