The area of sea animal sting or bite should be washed using salt water, according to Healthline, which also warns against exercise, using any medication unless prescribed by a medical professional and rinsing the wound with fresh water. The latter avoids spreading and aggravation of the venom.
When the sting is caused by jellyfish, Healthline suggests removing the tentacles with tweezers and flushing the wound with vinegar to stop the poison from spreading. Vinegar helps dissolve the spine of a sea urchin, while soaking the injured body part in hot water relieves the pain. Both MedlinePlus and Healthline suggest seeking medical help in case of severe symptoms such as breathing difficulties, chest pain, nausea, shock, swelling, excessive bleeding, injuries to the chest, neck or stomach or when the source of a sting cannot be identified.