Editing Surfing (section)

=== Rip currents ===
{{main|Rip current}} 
[[Rip current]]s are fast, narrow currents that are caused by onshore transport within the surf zone and the successive return of the water seaward.<ref name=Dalrymple1978 /><ref name=Smith1995 />  The wedge bathymetry makes a convenient and consistent rip current of 5–10 meters that brings the surfers to the “take-off point” then out to the beach.<ref name=Scarfe2003 />

Oceanographers have two theories on rip current formation. The wave interaction model assumes that two edges of waves interact, create differing wave heights, and cause longshore transport of nearshore currents. The Boundary Interaction Model assumes that the topography of the sea bottom causes nearshore circulation and longshore transport; the result of both models is a rip current.<ref name=Dalrymple1978>{{cite journal |last=Dalrymple |first=Robert A. |date=1978 |title=Rip Currents and Their Causes |url=https://journals.tdl.org/icce/index.php/icce/article/viewArticle/3345 |journal=Coastal Engineering |volume=1 |issue=16 |pages=1414–1427|doi=10.1061/9780872621909.085 |isbn=9780872621909 }}</ref>

Rip currents can be extremely strong and narrow as they extend out of the surf zone into deeper water, reaching speeds from {{convert|0.5|m/s|ft/s||abbr=on|sigfig=2}} and up to {{convert|2.5|m/s|ft/s||abbr=on|sigfig=2}},<ref name=Smith1995 /><ref name=Bowen1969 /> which is faster than any human can swim. The water in the jet is sediment rich, bubble rich, and moves rapidly.<ref name=Smith1995 /> The rip head of the rip current has long shore movement. Rip currents are common on beaches with mild slopes that experience sizeable and frequent oceanic swell.<ref name="Bowen1969">{{cite journal |last=Bowen |first=Anthony J. |date=1969 |title=Rip Currents: Theoretical Investigations |journal=Journal of Geophysical Research |volume=74 |issue=23 |pages=5467–5477 |doi=10.1029/JC074i023p05467 |bibcode=1969JGR....74.5467B |url=http://chinacat.coastal.udel.edu/cieg682/protect/bowen-jgr69.pdf |url-status=dead |archive-url=https://web.archive.org/web/20100612115232/http://chinacat.coastal.udel.edu/cieg682/protect/bowen-jgr69.pdf |archive-date=12 June 2010 |df=dmy-all |citeseerx=10.1.1.463.6097 }}</ref>