Look for the Zodiac, its a marine or Seal dingy with engine.
Its at
http://www.dc3d.co.nz/Utopia/fairlady.htmscroll and look for Zodiac. To put dudes in boat there is a group thing but I never have good luck with it.So I just name the boat like PBR and in each of the involved units init fields put this moveincargo PBR and they should start in the boat. Remember that PBrs have a max of 6 ppl.
Also in the init field of all dudes put
this setunitpos "DOWN"
That might work,or you could try puttting a waypoint on the commander, like right on him and make it a move and make his behaviour Danger in the waypoint settings. And make the formation wedge.
I'm not sure how to get your boat to do the comeback thing. Maybe try two boats. One that drops you off and leaves then make another with a waypoint on it like move or something, then make the load waypoint for it. Then put a trigger down that is activated by anybody and make alpha the code word. Then synchronize it with the boat's waypoint that is directly over it.
On alpha the second boat should drive over and pick you up and proceed on to the next waypoint to your end place. Another waypoint is needed for boat to leave its load postion.
Hope it works. Unless the more enlightened here shut me up with their knowledge....