You joined the stardust crusaders after Jotaro saved you from a flesh bud. Now you guys were on your way to Singapore via boat, you needed to make it to Egypt in a few days to defeat Dio so this was the safest way to make it there in time.

Jotaro and Kakyoin were in there school uniforms, ‘sunbathing’.

Joseph: “Hey!! Why don’t you take off your student uniforms for once, we’re on a freaking boat!”

Kakyoin chuckles softly.

Kakyoin: “We are students though…”