Traveling through waterways is definitely the oldest and one of the most efficient ways of travel, but not necessarily the smoothest. The need for a system for an endangered ship to seek help while it is ＿＿（51）＿＿ in the middle of an ocean has been felt ever since the first voyage happened. Since long, various forms of emergency signals have been used. One of the most commonly used ＿＿（52）＿＿ signal is maritime signal flares. These flares when fired ＿＿（53）＿＿ a minute indicate a ship in extreme danger and asking for help. This, however, is the form used today, an earlier version of ＿＿（54）＿＿ was developed by Martha Coston based on a framework laid by her deceased husband around 1850s. Coston's system underwent many modifications and was later ＿＿（55）＿＿ by the American marine services and standardized to be used all over America. Thanks to Coston's invention, ships now has much more to rely on when they run into troubles in the ocean.