Jellyfish

Clearing the area of jelly, tentacles, and wetness further reduces nematocyst firing. Scraping the affected skin with a knife edge, safety razor, or credit card can remove remaining nematocysts.
Beyond initial first aid, antihistamines such as diphenhydramine (Benadryl) can control skin irritation (pruritus). For removal of venom in the skin, a paste of baking soda and water can be applied with a cloth covering on the sting. In some cases it is necessary to reapply paste every 15–20 minutes. Ice or fresh water should not be applied to the sting, as this may help the nematocysts to continue releasing their toxin.
• Overpopulation
Evidence in recent years suggest that the population of jellyfish has swelled as a result of overfishing which reduces the number of predatory organisms that feed on them. This has allowed jellyfish to proliferate to the extent that they adversely affect humanity by interfering with public systems and harming swimmers. Jellyfish blooms cause problems for mankind. The most obvious are stings to humans (sometimes deadly), and causing coastal tourism to decline. Other problems are destroying fish nets, poisoning or crushing captured fish, and consuming fish eggs and young fish.