Gary Robertshaw
Coast Guard vessel training at Morro Bay Harbor entrance, December 2007. Photo: Gary Robertshaw.

The Dual Nature of Jetties

Whenever humans seek to control the environment, the smackdown can be severe and unpredictable. Nowhere is this more obvious than in the sea. Here, the ocean teaches us the folly of our plans, sometimes with fatal consequences. Jetties are prime examples. Built to create harbors and to control beach erosion, the disconnect between design and reality are often stark (Pilkey and Dixon, 1998). With respect to surfers, although there are downsides, we generally come out on top, as jetties create some of the best human-made waves on the planet. But for vessels entering and exiting harbors, jetties can be both a blessing and a curse. So here’s an example of two things we’ve learned from jetties: 1) How they have created some great surf spots; and 2) Some of the tragedies and near-death experiences created by jetties.

Death’s Doormat: Morro Bay’s famous jetties

One of the most famous images associated with Morro Bay’s jetties is a photo of the 84’ long M.V. Mojo, chartered by Hollywood star, George C. Scott’s during a massive winter storm on January 28, 1978. Ignoring warnings not to attempt leaving Morro Bay, the impatient Scott demanded that his skipper head out despite the risks. The result was an iconic photo of a near-death experience at the legendary Morro Bay harbor mouth that cost the owner $85,000 in repairs. Luckily, no one was killed and injuries were not life-threatening.

M.V. Mojo chartered by Hollywood actor George C. Scott, attempts to leave Morro Bay Harbor in 1978. For scale, the vessel was 84 feet long Photo: Scott Redd.

Morro Bay’s jetties are well known for dangerous conditions and are called “Death’s Doormat” by the local newspaper. Each year in the 1980s and 90s, the jetties claimed at least two lives. Because of that, it is near the top of the Coast Guard’s list of dangerous waterways.

Morro Bay in 1936, before the jetties were built. Notice the causeway out to Morro Rock. Source:

Historically,  Morro Bay was a natural harbor that allowed limited entry by small boats into the bay. In 1933-35 a causeway was built out to Morro Rock which was used as a quarry for building material. The jetties were built in 1942-43 to support naval training and patrol craft.  Due to large storms, the north jetty was damaged and repaired in 1943, 1944, 1946 and 1983. Major El Niño storms in 1983 caused $1,430,000 in damage to both breakwaters (Bottin, 1988).


From the air the jetties look fairly straightforward: they face SW, away from large winter swells, but like most jetties, they alter the flow of sand which creates a shallowing at the entrance to the harbor that requires dredging, which happens, on average, every other decade.

Screenshot 2018-04-14 18.28.53
Days where waves broke across the harbor mouth. From Kaihatu et al., 1989.

When swells are big, generally from Nov-Mar, the waves can break across the mouth of the harbor, and combined with strong tidal currents from the bay, make it very difficult (or impossible) to enter or exit the harbor. According to the Army Corp of Engineers, this happens about 28 days per year, on average (Table 1; Kaihatu et al., 1989). To make matters worse, winter swells arrive at a different direction than the opening to the harbor, requiring a turn across the prevailing swell direction which can push a vessel into the south jetty or into the surf down the coast. Lastly (as if that wasn’t enough), wave reflection off the end of the north jetty creates a cross-wave double peak at the entrance (see below), creating an additional unpredictable hazard that can be difficult to navigate.

Morro Bay Entrance. Photo: Woody Woodworth.

In fact, that’s exactly what happened on Feb. 16, 1983, during the famous El Niño storm year when the 44′ whale watching boat, the San Mateo, headed out with 32 passengers, including 23 Middle School students. Despite repeated warnings not to exit the harbor, the boat was hit by three large waves at the entrance and capsized, sending everyone in the water. None were wearing lifejackets.  As reported in the SLO Telegram-Tribune, at the time, then harbor patrolman Jerry Mendez stated: “With that many kids, with the conditions we had …” then he slowly shook his head. In his many years of patrolling the harbor, about half of the people on boats that capsized ended up drowning. Miraculously, due to the near-instant response of the Harbor Patrol, who had watched them head out and tried to warn them, with assistance by the Coast Guard, everyone was saved within 30 min.

Ironically, the city of Morro Bay was sued by insurance companies and survivors and settled out of court to minimize costs.  Many consider Morro Bay one of the most dangerous harbors in the nation: from 1979-1987, 21 lives were lost in boating accidents. Finally, in 1995, the Army Corps of Engineering deepened and expanded the channel to improve safety but there are still many days when it is impossible to cross the harbor mouth.

This situation isn’t uncommon in the US and other dangerous harbors include Humboldt Bay, California; Coos Bay, Oregon; and Oregon Inlet in North Carolina. For a detailed look at the history of Oregon Inlet checkout Pilkey and Dixon’s book, The Corp and the Shore.

Although the Morro Bay jetties create several surf spots — Widow’s Wall, Corners and South Jetty, all decent waves — they are not comparable to other famous jetty spots such as the Ala Moana Bowls, Newport Wedge, Santa Cruz Harbor, and the Santa Barbara Sandspit.

Accidental Wave: Santa Barbara Sand Spit

Santa Barbara Harbor Entrance showing the Sandspit. Photo: Woody Woodworth.

Creating perfect waves is difficult, as evidenced by the failures of many human-made reefs (but check out Kelly Slater’s wave park). Interestingly, all of the best jetty waves were accidentally created by the Army Corp of Engineers in its efforts to create safe harbors for boats. Nowhere is this more evident than at the Santa Barbara Sandspit, arguably one of the best jetty-created waves.

Montage of historical photos showing the development of the Santa Barbara Sandspit after jetty construction began in 1928 (source):

In the case of Santa Barbara, the waves took decades to develop. The first jetties were built in 1928-29. Over many years, the southward transport of sand built up Leadbetter Beach that eventually overflowed into the harbor, and despite constant dredging, creating a sandbar at the harbor mouth in the 1960s, producing an amazing wave.

Montage of photos showing the wave at the Santa Barbara Sandspit as it enters the harbor (source):

It’s a very unusual wave. The hollow right-hand barrel begins with a huge backwash coming out at an angle from the breakwater that breaks over a shallow sand bottom in front of the breakwater rocks. The wave is dangerous and can get very crowded but offers a superb tube-riding experience. Here’s an excellent description from Surfline:

“Here’s how Sandspit works: a set will approach the breakwater, hit the backwash, jack up right in front of some craggy jetty boulders and spin-off down the line. The takeoffs are ridiculously steep and are often outright airdrops, so paddle into them like mad, hop up as soon as you can and look to pull-in from ground zero. When conditions are ideal, the wave is a straight tube, nothing else. No room for carves, reentries or floaters. Visualize Kirra, but on a smaller, colder scale. You’ll see a lot of kids trying to launch airs at Sandspit, but why risk flopping over an endless, mind-bending barrel? Tuberiding is the name of the game here, but it’s also a dangerous place to surf. Not only is the bottom extremely shallow and the lips like jackhammers, surfers have been known to get washed over the breakwater and deposited in fetus position on the other side. Watch that backwash.”


Short video of Sandspit during Hurricane Marie in 2014:

In summary, the ocean teaches us she is firmly in control and our powers to manipulate her are insignificant by comparison. The bottom line is that although jetties as human constructs are generally successful in achieving their goals, we are a long ways from mastering the manipulation of coastal processes.

For ultimately we must realize that the ocean is all powerful and there is a limit to what we can do. There is a very clear wall that can be reached where the ocean just says “No, you are not going to do that!” and you are pushed back or you die. It isn’t a malevolent action, nor a kind one, it is just the ocean being itself; indifferent to the activities of humans, indeed all living things. The ocean just is. The challenge for us is seeing the limit, seeing that wall. It isn’t visible or even obvious. But when you see it you will never forget it.


  • Bottin, R.R. 1998. Case Histories of Corp Breakwater and Jetty Structures. Coastal Engineering Research Center. Dept. Army. Report 1. 70pp.
  • Kaihatu, J. M., L.S. Lillycrop and E. F. Thompson. 1989. Effects of Entrance Channel Dredging at Morro Bay, California. US Army Corps of Engineers. Misc paper CERC-89-13.
  • Middlecamp, D. 2018. Waves crushed a Morro Bay tour boat and tossed 23 kids into the sea. How did they survive? San Luis Obispo Telegram-Tribune. Accessed March 25, 2018.
  • Pilkey, O. H. and K. D. Dixon. 1998. The Corp and the Shore. Island Press.
  • Swellbrains, 2016. California Perfection Last Week at Sandspit in Santa Barbara. Accessed April 24, 2018.

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