Sawfish: mining the forgotten forests of the sea

Sawfish Lake Kenyir.jpg
Did you know that some of the best hardwood can be found underwater? When people built hydrodams and created lakes in valleys to get quick, cheap power, they flooded the trees and essentially forgot about them. A small underwater logging industry has ensued, but no company has taken it as far as Triton Logging of Vancouver, BC.

Instead of sending human divers underwater, Triton built a giant yellow submarine called the Sawfish — a 5,500-pound unmanned logging device capable of finding, chopping, and floating trees weighing up to 200 pounds to the surface from deep underwater. When pictures of the Sawfish circulated the blogosphere in 2006, three years after its initial deployment, the sub was harvesting softwood on the west coast of Canada. It has since increased its fleet to four, doubled each machine's lifting power, and expanded its mission to underwater hardwood forests in tropical reservoirs in Southeast Asia, South America, and Africa. Join me and Jim Hahurst, Triton's VP of Marketing, for a photo tour of how the new Sawfish works.


Guided by sonar, video cameras, and GPS, the Sawfish dives down under the surface and finds forests to harvest.


Once it finds the tree, the Sawfish grabs onto the bark with its grapples, which are like giant arms. It inserts a rolled up airbag that bolts onto the tree. Compressed air inflates the airbag. The saw on the Sawfish then cuts the trunk just below the airbag and stays there as the usable part of the tree shoots up to the surface. Then it moves on to the next one. The new Sawfish is capable of cutting and floating up 50 trees per dive.

Airbags Surface.jpg

When the airbags surface, a boat corals the floating trees and pulls them over to a barge area, where they are then transferred to a tugboat that takes them to shore for processing.

Kenyir Logs 2.JPG

These photos were taken at a recent Triton mission in Kenyir Lake in Malaysia. "We got an invitation from the government to do this," Hahurst tells me. "Kenyir Lake had divers for underwater logging in the past, but they were keen to try out safer, more environmentally sound tech." The government gets a royalty and stumpage, but Triton gets full ownership of the logs.

There are about 300 million trees underwater, all of them lying still in a deep freeze, inert because the lack of air prevents them from sequestering carbon. "By putting these trees on the market, we potentially displace land-based logging," Hayhurst says. "There are 45,000 major dam reservations in the world, and we've identified the top 20 opportunities. This is kind of like mining, really — we know where the diamonds are."


  1. Lisa, is there maybe an order of magnitude or two missing from the weight that the sawfish can handle? 200 lbs isn’t exactly a cost effective target for logging.

    1. As per the article, it never carries the trees – it just carries tanks of compressed air and flotation balloons.

  2. Very interesting. One quibble, though.

    The lack of air also prevents them from rotting and releasing carbon. So from a greenhouse gas perspective underwater logging is not as good as sustainably harvested lumber. Some of this now-sequestered carbon will end up back in the atmosphere, and we can be pretty sure no replacement trees will be grown.

    It’s a rounding error on the total problem, but nobody should mistake this for being better in a climate change perspective than harvesting trees and then planting new ones.

    1. From what I’ve heard, the vast majority of these trees would be used in construction. The reason they are going after these trees is because when they were growing the world was colder and therefore the growing season was shorter, leading to denser stronger wood. Coincidentally this might also be the reason Stradivarius violins’ sound quality.

      Anyways since they’re being used to build things it’s not like they are going to end up back in the carbon cycle. At least not very quickly.

  3. I have to second the first comment, 200 lbs, even underwater, seems like very little weight. The logs in the photos must go 1000 lbs. Still, I enjoyed the article, it was one of those where you say “I thought they had been doing this for years”.

    Also, I would like to find out more about the primary downstream uses of this timber. Where does it end up, in kitchen cabinets or IKEA veneers or flooring or what?

  4. Some amazing photos there.

    Surprised they get to keep the logs in the Malaysian deal, is that how it works with normal logging?

  5. I can’t find the link right now, but Wired did a pretty interesting article about these guys a few years ago.

  6. This story reminds me of something I saw on TV about ten years ago, detailing a salvage operation on the great lakes (Lake Superior I believe). The logs were cut and then floated to the mill, however many of them sank. The recovered wood was very old and dense and they were using it to make instruments among other things.

    Stradovarius violins are remarkable not only for their wood, but also because of the varnish used which gave it the instruments their unique voice.

    This is a great operation and anyone who thinks it is bad hasn’t thought it out. These trees are probably at least a hundred years old and it’s reckless to destroy living trees (which would be otherwise capturing carbon) when their is perfectly good (if not better) wood standing dead at the bottom of a flood plain somewhere.

    William: Old growth hardwood is not sustainable. This wood is being harvested to for use, they’re not bringing it up to let it rot.

  7. huh huh. you said “hardwood.”

    I apologize and am completely willing to blame a lack of caffeine for my lapse in judgment.

    1. Hehehe

      I believe the Discovery Channel (or History Channel, I forget) on their show about Loggers talked a little bit about logging the underwater trees (though with not such cool equipment).

  8. @dculberson:

    Well, maybe I was talking about the above water shots.


    Ok, I’ve cleaned my glasses now, thanks for highlighting my gullibility. ;)

  9. “These are often sold as tonewoods. We used to sell banjo rims made from this wood”

    Sorry, I’m not following? What’s the relationship between a banjo and tone?

    Seriously, some friends have organized a Polka band with accordion and banjo. Frightening, to say the least.

  10. IronEdithKidd, weight is the difference between the mass of the tree and the mass of an equal volume of the surrounding media (in your case, air, in the case of these trees, water) so 200 pounds sounds about right.

    You can lift a bigger log under water than you can free-lift in atmosphere, kapische?

  11. regarding the lift capability of only 200 lbs, perhaps this is a typo, or maybe not. The logs may in fact be just less than neutrally buoyant, so this amount of force may be all that is required to surface them.

  12. This is one of those situations where it’s helpful to understand the difference between “weight” (especially the weight of something that’s under water) and “mass.”

    Of course the wording of the post adds to the confusion since it follows a sentence stating the (presumably) above-water weight of the submarine with a measure of its below-water lifting capacity.

  13. There’s also the practice of harvesting the multitude of sunken logs from old logging rivers, although I can’t find any links to pictures at the moment.

  14. As an aside,
    Water does pretty much the same thing with cultural artifacts. One of the great problems in archaeology is that organic materials do not survive contact with air for so long. Barring certain ultra-dry climates wet is good. In the Tennessee Val, it’s impossible to estimate the amount of pre-Columbian cultural remains that are under the surface of reservoirs etc. due to the actions of the TVA, but maybe they are still down there. Kickin it’ so to speak. You hear stories of collectors walking the mud flats during winters when they lowers the reservoirs.
    Really neat article…too :)

  15. They’ve been “mining” underwater trees forever. Pre-Revolutionary War Dutch farmhouses in the NYC area have roof shingles from cedar that were mined from swamps in New Jersey. They’re still in use, some 300 years on…

    1. They’ve been “mining” underwater trees forever. Pre-Revolutionary War Dutch farmhouses..

      Yeah.. but not with robots!

  16. Along the lines of what JoshP said, the same factors are what make the Great Lakes so awesome at preserving shipwrecks. There are ships that are fairly well intact at the bottom of the lakes that are well over 150 years old. Around 1900, several organizations tried lifting wrecks to display at on shore museums. The wrecks would then disintegrate in a matter of years.

  17. The wood is sought after by instrument makers. Guitars, violins, etc. The tonal quality of the wood is unparalled. They are coming closer and closer to replicating Stradivarius.

  18. On one hand the environmental benefit is huge – this allows more forested area to grow untouched (or lightly managed) while we are harvesting underwater wood. As far as logging tropical hardwoods, those are some of the most valuable and endangered woods so there is definitely a benefit there.

    On the other hand is there any damage to underwater ecosystems at the loss of this quasi-reef? Do water flow patterns or speeds change with this modification of the underwater topology? I’m not stirring up trouble (no pun intended), just curious if it’s been considered.

    1. That’s exactly what I was thinking. There’s this great habitat (that we admittedly created by flooding the plains) that wildlife are using. What happens to that habitat when it’s ripped up?

  19. They used to do the opposite in my hometown- they’d pay for Christmas trees that would get tied to a couple of cinder blocks, and get chucked in the lake. The smaller fish need somewhere to hide.

    For stuff that sank after being cut and floated downstream, this isn’t so much of a factor- no limbs. But for trees that were there when a reservoir was flooded, it’s a loss for the fishes.

  20. I’ve got a big stack of Port Orford Cedar that was sunk in a lake in the early 1900’s. Really fine grained stuff for musical instrument tops. Beautiful stuff.

  21. I work in the offshore oil and gas industry and in the deepwater arena, we utilize ROV’s for all of our subsea work, in water depths up to 10,000 ft. An ROV (Remote Operated Vehicle) is the technical term for that tree harvesting vessel. They are controlled from a surface vessel via a spooled umbilical…you can see it in the artists rendering above. It’s the yellow line trailing behind the ROV. The ones we use have fiber-optic controls and the video is amazingly clear and in color, too.

    I’ve also seen airbags used to float underwater pipelines, etc. A 500 ton airbag is not that large and I think the 200 lb figure given is a typo. Those trees have to be water saturated by now with very little, if any, air trapped in the cells. Once the empty air bags are attached, they are filled via a hose that is connected to a surface air compressor, not via compressed air tanks. The buoyancy on any ROV is critical…too much and it struggles to maintain depth, too little and it will sink like a rock. If compressed air is used, the buoyancy of the ROV would change as the air is depleted.

    I doubt if any old growth trees are used for construction, either. Old growth wood has tight growth rings and is much more stable than today’s trees. The wood likely goes to cabinet makers, artisans and serious woodworkers. The fast growth Pine forests are where the bulk of construction lumber comes from. Those trees are sustainable, too, and young trees consume more C02 and release more 02 than older trees.

    BTW, I work with ROV’s in my day job and my hobby is woodworking so that’s the source of my comments.


  22. It’s interesting to see wood being harvested this way. I’ve used maple harvested from Superior and it was interesting once it was fully kiln-dried – harder and definitely harder to work than ‘normal’ maple.

    And wrt to Strad violins/old wood: it’s not the varnish, it’s not the wood….he was a skilled builder, and built great instruments. The current crop of great builders sound as good or better. Good wood helps but it’s not the be-all and end-all….there is no magic wood.

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