Yes. Tough Mudder 5K, 10K, and 15K are not races and participants are encouraged to skip any obstacle they are not comfortable completing. The way we see it, you are there to have fun and challenge yourself. If you think a particular obstacle really isn't going to do this for you, just go around it - without a penalty or shame.
Anyone who is at risk of our electric-related obstacles (due to medical concerns) or cannot swim (and would have a difficult time in water) is strongly advised to skip these obstacles, as safety is held at a premium. Please speak with a doctor before coming to an event, as they can evaluate and advise you based on your specific circumstances.
Note: Race Series events only have a select few obstacles that can be skipped with a penalty. Please refer to the Event Info Pack (available a few weeks prior to the event) to see the specific rules.