1. Create a riffleman on land.
2. In its init box, enter: Zodiac = "B_Assaultboat" createvehicle [(getpos player select 0), (getpos player select 1)+1, (getpos player select 2)]
3. Preview the game, you will notice that the boat is right beside the player.
4. Now go back in the editor and just move the player in the water.
5. Preview the game, you will notive that the boat is something like 25 meters from the player.