Editor:
1. Place a diver over the water and make it a player's character.
2. Place a demolitions expert diver nearby.
3. Place a moored mine (Empty/Mines/Naval mine) close to both of them.
Ingame:
4. Make sure that the mine was spotted. Swim closer to it if necessary.
5. Aim at the mine and press tilde for a quick menu
6. Select "Disable mine"
7. The diver will say "roger" but won't do anything.
8. Get back to editor
Editor:
9. Place both divers and a mine exactly like before, but over the airfield's runway.
10. Use the same method to order the diver to disarm the mine.
11. Observe, that he acknowledges, crawls to the mine and disarms it.