Cocoa Beach - Resort on Cocoa Beach

Beach in front of the resort. Was in the water average of chest deep with the waves. Was about six feet from my 11 year old kid and she got stung on the arm. Fair amount of waves so couldn't see it. Thought I saw something dark with curly / grass like extensions about 10 minutes earlier in a wave crest. Staff at the resort were very helpful. Vinegar did the trick after an hour.