An 18-year-old who had washed on to the shore at Port Elizabeth's Wells Estate beach died on Wednesday evening in spite of extensive efforts to resuscitate him, the National Sea Rescue Institute (NSRI) said on Thursday.Jonathan Tufts, NSRI Port Elizabeth deputy station commander, said it seemed that two teenagers and a 20-year-old man were swimming when they were caught in rip currents."A 28-year-old bystander launched into the surf to try to help but he was swept away by rip currents," said Tufts in a statement.A 17-year-old made it to shore and was not injured, but the 28-year-old who wanted to help and the 20-year-old were missing. A massive search alongside multiple other emergency organisations was launched for them.A bystander had administered CPR on the 18-year-old who had washed on to the shore and paramedics had taken over when they arrived.However, after all efforts to resuscitate him, he was declared dead. Police have opened an inquest docket."The NSRI, on behalf of all services involved, convey their condolences to the family and friends of the deceased teenager."The NSRI explained on its website the tell-tale signs of rip currents are: Water through a surf zone that is a different colour to the surrounding water;A change in the incoming pattern of waves (often the waves are not breaking in a rip channel);Seaweed, sand "clouds" or debris moving out to the back where waves are forming through the surf zone;Turbulent or choppy water in the surf zone in a channel or river-like shape flowing away from the beach. A rip current channel is often deeper than the surrounding area so be aware that you can suddenly find yourself unable to stand. When you go to the beach, save the NSRI number displayed in that area in case you need to call for help.Or, call 112 from a cellphone. The NSRI produced this explainer on what a rip current is and what to do if you find yourself in one. There is also this video and these pictures taken from the air for you to see what rip currents look like when you go swimming. The NSRI advises swimming at beaches where there are lifeguards who can help in an emergency.