What causes sea foam?

Stu Nettle picture
Stu Nettle (stunet)
Swellnet Analysis

Overnight the surf world learnt of the death of five Dutch surfers. They were amongst a group of nine who paddled out at Scheveningen during a large storm and were overcome by beds of sea foam.

Early reports said the foam was toxic and alluded to death by poisoning, however at least two of the surfers showed signs of asphyxiation. A tragic result caused by what's usually harmless matter.

Sea foam naturally occurs whenever saltwater is agitated. You may have seen it on rocky coasts, where waves break abruptly onto rocks and a line of spume then drifts downcurrent, or down the line on big days where wave action alone creates the foam.

Turbulence makes the impurities in saltwater - some of them naturally-occuring such as salts, proteins, fats, and algae, but also additives such as detergents and other pollutants - to bubble and froth. It can happen on a very small scale, but is more noticecable when either the waves are big, or the surface is agitated by strong winds.

Most sea foam is only a few inches thick and begins to break up and settle shortly after it's created. However, given a mixture of a fresh water source, particularly from a river that contains organic materials, and a surface blend of storm waves and strong wind, sea foam can grow two to three metres high. It then begins to create it's own environment, the bubbles bonding stronger and lasting longer.

In Australia, this often happens during storm conditions in SE Queensland and northern NSW, where many large, freshwater rivers empty out into the sea. Associated rainfall swells the rivers, and the floodwaters mix with the churning sea to make banks of sea foam. Depending on the direction of the wind it can also blow inland smothering all features.

In 2013, the wind and waves from Tropical Cyclone Oswald mixed with freashwater from the Maroochy River to create large beds of sea foam:

While it looks fun, there are some hidden dangers. In 2015, Ben Redman, then-director of Far North Coast Lifesaving, told The Northern Star that, "foam usually results in a large number of snake sightings."

"People shouldn't swim in it," said Redman. "You'll usually find a lot of sea snakes in the foam, they seem to be attracted to it."

In 2008, claimed Redman, they counted 21 snakes during a sea foam event at Ballina's Lighthouse Beach.

Most sea foam is harmless to humans, however as it can be caused by many ingredients, most of them invisible, it's impossible to say with certainty that it's safe. Agricultural runoff or urban pollutants may be causing the foam, and hence making it harmful to humans.

If you've ever swallowed sea foam, you'll know it's highly irritable, but death by asphxiation is rare. While it may seem implausible, there's very little air in the bubbles, mostly organic aerosols and toxic aerosols. The foam displaces the air from above the water surface like a gentle avalanche. If this happens amongst breaking waves...breaking waves that you can't see, then the danger is obvious.

Consider that during the Scheveningen tragedy, the authorities had to use a hovering helicopter to move the sea foam and continue their search.



GuySmiley's picture
GuySmiley's picture
GuySmiley Wednesday, 13 May 2020 at 3:28pm

Sea snakes!

Yendor's picture
Yendor's picture
Yendor Wednesday, 13 May 2020 at 3:32pm

Jesus, to lose your life for a surf at Sheveningen! Average at best and mostly pretty dire. ( I speak from experience) Those poor Dutch surfers don't have much

indo-dreaming's picture
indo-dreaming's picture
indo-dreaming Wednesday, 13 May 2020 at 4:21pm

Reminds me of the good old days of the bounty foam parties.

Womble123's picture
Womble123's picture
Womble123 Thursday, 14 May 2020 at 9:04am

@indo-dreaming the new or old bounty......?

Nick Bone's picture
Nick Bone's picture
Nick Bone Wednesday, 13 May 2020 at 4:38pm

Anecdotally, when I've encountered sea foam, it's usually a thin layer but what stands out is that it feels like I'm in a recording studio and there is a sort of deafness around. I can't hear others as clear and it's that dense sound/feeling of quiet. Anyone else?

nicksanta's picture
nicksanta's picture
nicksanta Wednesday, 13 May 2020 at 6:22pm

It'll be similar to the eerie silence of riding powder days.. Snow is an extremely effective sound dampener.

Sea foam likely has very similar properties

josh.wright's picture
josh.wright's picture
josh.wright Friday, 15 May 2020 at 5:37pm

Likewise. There was a lot of foam around during a recent cyclone swell and I experienced exactly the same thing at that time

memlasurf's picture
memlasurf's picture
memlasurf Wednesday, 13 May 2020 at 5:22pm

My son said he went to some really dodgy foam parties at Sky Garden I think in Bali. The foam ended up being a nice dark grey colour.

SI's picture
SI's picture
SI Wednesday, 13 May 2020 at 5:27pm

I once paddled out by myself near Kirra during the onslaught of a cyclone, when I was a teenager, I was bored and just wanted to see if I could make it out the back. Winds were bending trees and there was heaps of the foam. There were two breaking zones for waves. One close in - a band of around 100m I guess of breaking surf, then there was a band of around another 100m behind it of deep water without waves, and then around 50-100m of bigger waves out the back, around 8-12ft. These stormy conditions are dodgy, not only for the foam. I passed the inner zone and paddled through the deep section and then waited for a big set out the back. After the set, I paddled as fast as I could to see if I could clear the outside section. I got through a few waves and it looked like I was gonna make it out. But then I noticed a couple of big dark waves forming out the back. They grew bigger and more imposing and I hesitated. I thought they were going to break in front of me so I turned around and started paddling in to avoid the full impact, but then as I paddled in I noticed that they still seemed happy travelling further in, so I turned around again. This time I really committed to getting out, but unfortunately the first one broke about a few metres in front of me. I dived down and it hit me pretty hard. It then put me through a badass washing machine cycle, but there was no coming up. I just kept spinning with no sense of up or down. At one point after a long time under water, I was thrust in a circular motion up and out of the surface water and caught a breath, and lucky I did, because a moment later I was sucked violently back under and into the whirlpool (hey that’s a washing machine brand isn’t it?). Anyway, the spin cycle went on for a good while longer and then I came up. When I came up, I looked around and I reckon I had shifted sideways down the beach about 300m, but the startling thing was I was in on the beach area. This means that I had travelled right through around 100m of deep water with no waves breaking in it. But underneath the that deep water there was like a frigging underwater cyclone churning. It looked fine on top, but underneath it was fucking psycho!! I nearly drowned in water that had no waves breaking in it!! So yeah, I’d definitely think twice about paddling out in active cyclone conditions again- not going to happen... I should have really worked it out with the wind bending trees sideways and the foam all over the ocean and beach, but there’s something about the teenage search for boundaries and the lack of concern about risks. Haha, luckily I’m still here to tell the tale!

Yendor's picture
Yendor's picture
Yendor Wednesday, 13 May 2020 at 5:45pm

We have had cases here in NZ of sea foam causing quite a few allergic reactions when it's been formed in algal bloom conditions. Breathing difficulty, coughing and the like. This was for people just walking on the beaches. Health advice was to stay away from those beaches. Blooms seem to encourage foam formation too.
I know when I've had a mouthful of foam after a wipeout it's horrible. It seems like it gets into your airways easier than sea water and leaves you spluttering.

fishnsurf's picture
fishnsurf's picture
fishnsurf Wednesday, 13 May 2020 at 7:02pm

Maybe its time for wave pools to become mandatory in all nations .

Lottolonglong's picture
Lottolonglong's picture
Lottolonglong Wednesday, 13 May 2020 at 7:03pm

2016 black noreast swell saw Olympic pool sized patches of that stuff floating thru where I was out on the Monday
Watching top to bottom 10-12ft barrels grinding down the point was epic, listening to the sound of those lips cracking out in the flats was loud and occasionally a foam patch would drift into the impact zone and the muffled sound was next level, something I will never forget

wally's picture
wally's picture
wally Wednesday, 13 May 2020 at 7:59pm

With the 2013 Alexandra Headlands sea foam situation, it’s worth watching this 20 second video.
A bus wading thru, then there’s a bit of a surprise in the last 10 seconds.

tubeshooter's picture
tubeshooter's picture
tubeshooter Wednesday, 13 May 2020 at 9:16pm

Not really my idea of enjoying a frothy one

Thegrowingtrend.com's picture
Thegrowingtrend.com's picture
Thegrowingtrend.com Wednesday, 13 May 2020 at 9:34pm

Bounty foam gave every one pink eye one night..

views from the cockpit's picture
views from the cockpit's picture
views from the ... Thursday, 14 May 2020 at 10:48am

Foam partys or Espuma festas were all the rage in the Algarve late 80's-90's.
Always wore dirty shoes in there for a wash.
Some wild shit went down in that foam ;-)

ringmaster's picture
ringmaster's picture
ringmaster Thursday, 14 May 2020 at 4:10pm

'Some wild shit went down in that foam ;-)'

Knowing you as I do Viewboy, I don't doubt that at all........

zenagain's picture
zenagain's picture
zenagain Thursday, 14 May 2020 at 7:22pm

What's a Bounty party Indo?

truebluebasher's picture
truebluebasher's picture
truebluebasher Friday, 15 May 2020 at 4:26pm

Great story & links ...
Sea Foam now has untold agitators...
Golf Courses, Airports, sewage outfall all feed foam to the Ocean.
Offshore Shark Nets, Desal Pipes, Ships, Oil /Gas Rigs all agitate foam.
Cyclonic Lows & Hurricanes swamp & whip the lot together as a Toxic Brew!

To this Mystery at hand, it sadly may have been an accident waiting to happen! {r.i.p}

Scheveningen harbours Green Flagships that whip up a flurry of foam.

Like all here... tbb was mystified by surrealistic Foam coating over the seawall.


That does not look natural & that is because this city ramps nature.

*Scheveningen Wastewater Plant hugs the Harbour.(Unusual for a Tourist Town)
3 effluents stacks + Freshwater releases daily in a short turbulent flow (Foam)
The system naturally stinks the beach & all manner of biotics are blended as a cure.
sorry ! Link won't click in...bummer! (Was about cleaning the harbour process)
tbb is implying that the Harbour is accelerated...resulting in foam.

*Geo Thermal Plant sits just inside the Harbour the 20ML day/inflow inox pipe.
The Ammonia pump outflow pipe also agitates the harbour.
Note Pipe Volumes are no large but less deep than Desal (Can suck in surface foam)
The Sea Power Scheme alters harbour Temperature -Winter 4* > 11*.
Summer 21* (rec 1963) cools + warms 5km of towns house slabs...50% less Co2

The Town recently added Wind / Solar / Desal to prolong the Ocean energy supply.
Desal pronounced Saline Outfall is also known for Foam.

Main point being that most Cities can afford to space this out..
Here we see a small harbour/ huge pier being agitated by 2 inflow / 5 out flow pipes.
That is a washing machine already as well as a dual Seafoam straw.

Not Enough Foam Agitation on the foreshore, let's go for a paddle...

2020 Off shore Oil & Gas Platform fits Electrolyser to produce Hydrogen & Oxygen

No other city in the world has gone to these lengths of altering their ocean.
The Foam we see is most likely of their own making...that's a double tragedy.
tbb is not implying that's it's highly toxic by nature but by sheer haste of supply.
Everything came together for a perfect storm...
Whirling Dervish of warmer larger waves stirring foam clogging pipes regurgitating.
This town can clearly generate foam faster during a storm & that's on show!
Just where would you start & there is no end with that much foam contribution.
tbb is jumping ahead, but thinks the town will need to re-examine eco pipelines.

If that story isn't startling enough...here's the flip ~100% natural Sea foam mystery.

Being a mystery tbb thought to load the audio version as it's more inviting.
tbb: Only lets on it's a wildlife incident ...Less said the better! No Spoiler (Enjoy!)

March 2012 ~ NOAA (Episode 93) Solving the Sea Foam Mystery...{ tbb ***** }

Backup Menu Page ...just in case it goes spazz...(re: heaps of cool episodes).