I think everyone has pretty well covered the liability aspect of this. I would like to add my perspective as a collegiate skier. I am very supportive of collegiate skiing and want to see it grow. Most of us are responsible kids just looking to get some bouy time. However, as it has been said there are a few spoiled, disrespectful and inconsiderate collegiate skiers out there. If it was my lake I would want to meet with the team and spend some time with the leadership. If they seem like responsible kids then let them ski but make it clear that if they abuse the relationship than the deal is off. Also, make it clear that you have the option to ban specific members of the team. I have seen teams take tons of pride in maintaining their boat/site and I have seen other team destroy a boat/site in half a season. Meet with the team and try to figure out if these are the good ones.
Another options is to take care of the liability but instead of an open invitation just invite them out every once in a while when you feel like being charitable.