[KJS]

you can disabledefmovement

or if it goes on a npc you can say

drawunderplayer;

(I have never tested that out if you walk or swim)

or you can change the default gani of swim to walk with the new npc command replacegani
it would be like

replacegani swim,walk;

(you would do that for how ever long you wanted them to be on it)

then you would do after they got off the spot or something do this

replacegani swim,swim;

well this will count them as swimming in the coding like
if(onwater(x,y))

it would say it is on the water, but it would set the ani so it looks like they are walking...