You need 2 players and one boat.

Please follow these steps to reproduce:

1. The first player (player A) has to sit in the boat.
2. The seoncd player (player B) sits on the "passenger seat"
3. Player A presses A- or D-key until the boat spins
4. If the boat spins fast enough, player A has to leave the boat (SHIFT) while spinning
5. Player B will automatically be placed into the first boat slot/seat.
6. Now player A has to sit down into the boat again (now on the passenger seat) and his head will start to spin.

Done.

Video:

https://youtu.be/eHMCPk8q6oU