water only tag on creatures

[swillo]

Is it possible to have a check box on the creature properties that limits them to moving in the water. Just like we can't fight in the water, I was thinking of having creatures that only swim in water. Making crossing it more dangerous. Like sharks or Parana or water serpents. Since they can already move under the water it would make them look like they are swimming, but I just wouldn't want them to move on land.
Maybe I need to set their run speed to -1 and swimming to 99?