How to prevent nose piercing infection after swimming?

I just got a nostril piercing 4 days ago which I've been trying to get for months. However, I forgot I have a trip in 2 weeks to swim with manatees. I understand the risk of swimming with a new piercing but I already paid for the trip and I really don't want to have to take the piercing out. What advice is there for preventing an infection after swimming, especially in open water? What is the likelihood of infection? Are there any protective covers I can wear? I also recently started judo and would like to continue without having to take too long of a break. Is it okay to cover the piercing with a bandaid to protect it?