There is a tsunami in the middle of the open sea. Luckily there are no ships around, so the tsunami in the middle of the open sea is not damaging to anyone.
Someone dares you to go out to the open sea and surf on the middle of the tsunami. “Oki (おき) doki,” you reply. You can’t refuse a dare. Every time someone dares you to do something, you always respond with “oki doki”.