Being fully recovered going into a competition day is obviously very important to ensure top performance. Although everyone is different taking an active recovery day the day before competition is a very effective way to ensure that your recovery will be adequit. Taking the day right before the competition and doing a workout that will challenge your respiratory system without breaking the body down will help "prime the system" for a very intense workout such as the crossfit open. However, i do not reccomend completely taking the day off. Often times completely taking the day off will result in the the athlete coming out flat because the body and nervous system isnt warmed up and ready to hit peak performance. Below is a great workout that will serve as a great recovery workout.
Swim 1 length on Every 30 seconds untill failure
Rest 2 min