What is a riptide? Phenomenon explained after Bournemouth deaths - including what causes one and what to do if you get caught<br /><br /><br />Locals are still reeling from the deaths of two children at a packed Bournemouth beach last week. <br /><br />Sunnah Khan, 12, and Joe Abbess 17, drowned on May 31 after reportedly being swept from a sandbank, while eight other beachgoers got into difficulty in the water.<br /><br />Although Dorset Police are yet to work out exactly what happened, a father of one of the survivors said his daughter was one beachgoer carried by a 'riptide' near the pier.<br /><br />While this is unconfirmed, Dorset Police said an investigation is 'looking at all circumstances' including weather, wind conditions and the state of the water.<br /><br />Here, MailOnline looks at the science behind the phenomenon – and the best way to act if you ever get caught in one. <br /><br />Rip tides, more accurately known as rip currents and also known as simply 'rips', are fast-moving channels of water that move away from the shore and towards the open sea. <br /><br />They can reach speeds of up to five miles per hour - faster than an Olympic swimmer - making them a leading surf hazard for all beachgoers. <br /><br />The National Weather Service explains: 'Rip currents form when waves break near the shoreline, piling up water between the breaking waves and the beach. <br /><br />'One of the ways this water returns to sea is to form a rip current, a narrow stream of water moving swiftly away from shore, often perpendicular to the shoreline.' <br /><br />Although a father of one of the survivors said his daughter was carried by a 'riptide', the more accurate term for these sorts of currents at beaches are simply 'rip currents'. <br /><br />Gerd Masselink, a professor in coastal geomorphology at the University of Plymouth, told MailOnline: 'Rip currents are often referred to as rip tides – this is an incorrect term and we have been campaigning for decades to get rid of the term, to no avail.'<br /><br />Professor Masselink is part of a research project looking specifically at rip currents at Bournemouth – which are common there – and their link with coastal structures. <br /><br />
