Stung by likely a box jellyfish

While swimming offshore i suddenly felt a strong sting, felt like an electric shock. Despite the water being clear, i could not see any jellyfish so i assume it was a box jellyfish. I was left in strong pain and muscle cramps, symptoms of box jellyfish sting. Apparently Alatina jellyfish live in this part of the indian ocean, so that could have been what stung me.