Any disruption such as harrassment may cause the swans to leave the area permanently. So, if you want them to stay you will need to be subtle in your efforts. First, is the raft removable for several days? If so remove it and offer the swans some food ( lettuce, bread cracked corn and poultry layer pellets) in the area but away from the raft. If the raft is not removable, try to make the raft uncomfortable for the swans ( i.e. place cardboard boxes or other material that will not fall on the birds or trap them. The object is to prevent them from hurting their feet or legs when trying to climb onto the raft. Of course, you may need to be close by so that no injuries occur or the material does not fly off into the water etc. Then, feed the swan family in another area. If this does not work, you will need to wait some time for the birds to get tired of the raft and move on. Good luck and let us know how this situation progresses. The Regal Swan