The ESN Sea Battle is an international cruise brought to you by ESN Sweden. The cruise takes place twice a year, once per semester, between Stockholm and Tallinn. Each event has around 2100 international participants, and the officially participating countries are ESN Sweden, ESN Denmark, ESN Norway, ESN Estonia, ESN Latvia and ESN Lithuania.

All program on-board is free for participants, and includes karaoke, speed dating, treasure hunts, salsa lessons, and competitions among others. The cruise has three dance floors and also the ferry company organizes shows aboard. You can also find a tax-free shop on board.