I want to swim/snorkel in the river and the blue hole in the State Park in Florida, BUT....?

I want to swim/snorkel in the river and the blue hole in the State Park here in Florida. They let many swim in the river and blue hole everyday. Here is my dilemma, I want to bring my lower leg knife with sheath in the water with me when I snorkel.. They said, its not allowed. I said, what if an alligator decides to attack me and I need to defend myself.. They said, there are no alligators in there, which is such BS.. They can't guarantee my safety, yet they won't let me bring the knife to protect myself.. This isn't fair! I asked if I could bring a small steel staff with point - they said NO, no heavy metals allowed in the water.. Please Advise?