There are various problems here but the conceptual one is that you haven't thought about who is going to drive the boat.
Is the group led by the player? Is the player going to be the driver?
Anyway, try this:-
Delete the moveincargocommands.
Delete the triggers and engineOn commands.
In the init field of the unit you want to drive the boat write,
this moveInDriver floatie; this assignAsDriver floatie
Group the boat to the group leader.
Change the special field of each unit including the driver) in the group to "In cargo"
Edit: your English is just fine. :thumbsup: