sentences:  The line arrow was invented by Lewis Holzendorf and developed by Forrest Wilson at the Cave diving NSS workshop, inspired by Sheck Exley and other cave diving pioneers, and later, a few hundreds of the handmade markers were sold through Branford Dive Center in North Florida.Soon they became very popular and today are commonly used by underwater cave explorers.Line markers are generally used on permanent guidelines to provide critical information to divers following the line.