Probably you have reached the mission in GTA V where Trevor needs to “sit on a boat”?
It’s the mission where all the three characters need to work together.
This mission in GTA V involves a train and a boat.
Michael will tell Trevor to sit on the passenger seat.
To do that, while you control Trevor, get up on the boat and press the “F” button, like you do when you enter a car.
This is pretty much all you need to do.
This simple action can be very confusing and players might try a lot of buttons in order to get Trevor to sit on the boat.
But this is how you do it, pressing “F” on PC.
If you are on a console like PS4 or PS5, press the triangle on the joystick.
For Xbox, probably it is similar, press one of the four action buttons from the joystick.
Now you know how to finish the Trevor GTA V sit on a boat mission.
If you have any more questions, please leave them in the comments section.