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Rogue, or freak, waves are another matter. They can arise anywhere in any sea condition, in heights from 50 to 100 ft or more, endangering even the largest ships. <ref>French Research Institute for Exploitation of the Sea, http://www.ifremer.fr/metocean/rogue_waves.htm/</ref> <ref>http://www.sciencenews.org/pages/sn_arch/11_23_96/fob2.htm/</ref> <ref>Science News Online, Science News, http://www.science-frontiers.com/sf066/sf066g14.htm/</ref> Until recently they were thought to be rare but most common in the [https://en.wikipedia.org/wiki/Agulhas_Current Agulhas Current] off the Cape of the same name on the southeast coast of South Africa, between Durban and Port St. Johns.<ref>Wikipedia, http://en.wikipedia.org/wiki/Freak_wave/</ref> <ref>SA Sailing Directions Vol 1 page 43, http://www.dynagen.co.za/eugene/freaks.html/</ref> Freak waves, rogue waves, extreme waves and ocean wave climate, Kristian B. Dysthe, Department of Mathematics, University of Bergen, Norway, et al, http://www.math.uio.no/~karstent/waves/index_en.html/</ref> <ref>Understanding the Freak Wave, Dr Paul Taylor, Department of Engineering Science at Oxford University, et al, http://www.epsrc.ac.uk/ContentLiveArea/Downloads/Adobe%20Portable%20Document%20Format/E-TaylorP.PDF</ref>

<tr><th colspan="3">Waterline Length vs.<br />Significant Wave Height (ft)</th></tr>

<tr><th>Boat<br/>LOA</th>

Even coastal waves can become rogues. Waves have been observed on the Alabama coast as high as 32 m; while coastal 30-ft waves are frequent in Maine.<ref> Vijay Panchang, Texas A&M University at Galveston, www.tamug.edu/mase/wave_file/wave%20%simulations.htm</ref>

== Reserve Buoyancy ==

Freeboard, the distance from the waterline to the edge of the highest watertight deck amidships, is a rough measure of reserve buoyancy. Typically buoyancy is lost when the edge of the freeboard meets the water.