To fight creatures that normally live on land in water, go to the water around Cinnabar Island or Seafoam Islands (The only place you can be randomly attacked while swimming.) Swim along the shore of any island and you will fight land creatures. (You have to swim on a place where the square is half land and half water.)

Instead of fighting a set group of monsters in the water, you actually fight monsters from the last place you were. So to get safari zone monsters, you need to go to the section of the safari zone with that monster, let your time run out, then go to the coast. Using this trick I have caught Kangaskhan, Scyther, and Tauros!