Here is the full list of all 15 Summer Trip Cruise achievements.
Complete all Greece trips
Complete a trip with 3 stars
Crash while being swept away by water currents
Reach the finish line with only 1 piece of the cruise ship
Reach the finish line with 10 seconds to spare
Complete the first trip
Complete all Italy trips
Complete all Spain trips
Complete all Greece trips with 3 stars
Complete all Italy trips with 3 stars
Complete all Spain trips with 3 stars
Honk the horn for a while
Go at full speed for 10 seconds
Crash with a barrier
Crash with a moving boat