Re your question, What do English collge students do in summer holidays? Do you mean "British"? Or, does this include all students in the "English speaking" countries?
A very large number of college students in the United States wish to work at a job during their summer holidays to help pay for their college education. The expense is "huge" - running to many thousands of dollars for most of them. Scholarships and/or student aid aside.
What do you and your friends do? And what country do you hail from?