Ocean carbon removal
Grown in sunlight. Stored in the dark.
Tidewater farms offshore kelp, sinks it below 1,000 metres, and sells only the tonnes our sensors — and our auditors — can prove.
(01)6 mSunlit shallows
This page is a thousand metres deep. Keep scrolling and you’ll make the same trip as every tonne we sell — from a kelp blade in the sunlight to the cold floor of the ocean, where carbon stays put for centuries. We measure it the whole way down.
The depth gauge keeps count. We’ll tell you when you hit the floor.
Most carbon credits ask you to trust a forecast. Ours are issued after the fact: grown, sunk, landed, measured, audited. Only then do they go on sale.
(02)12 mThe canopy
Three steps. The third is why we exist.
Kelp is the fastest-growing forest on Earth, so growing it is the easy part. Proving where its carbon ends up is hard — which is where most of our budget goes.
- Step 01
Grow
We seed native giant kelp on submerged rope lines twelve kilometres offshore. It grows up to half a metre a day, pulling carbon out of seawater that then draws more down from the air. No fertiliser, no freshwater, no farmland.
- Step 02
Sink
At peak biomass we harvest, bale and ballast the fronds, then release them over water deeper than 1,000 metres. Down there, cold and pressure keep the carbon out of the atmosphere for centuries.
- Step 03
Verify
Sediment traps, seafloor cameras and pH sondes follow every batch down. An independent auditor reconciles the data before a single tonne is issued. If we can’t measure it, we don’t sell it.
(03)80 mThe ledger
Last verified 3 h ago
Every tonne has a serial number. Every serial number is public.
184,262t
Verified & issuedTonnes of CO₂ removal in the Tidewater registry since Q1 2024.
3,140ha
Under cultivationHectares of kelp on submerged longlines along the Tidewater Shelf.
7sites
Active farmsEach paired with a sink site past the 1,000 m line.
Since you opened this page our canopies have drawn down 0.0 kg of CO₂. None of it is for sale — it hasn’t sunk yet.
Tidewater Public Registry
| Batch | Site | Landed | Depth | Tonnes | Status | Retired by / note |
|---|---|---|---|---|---|---|
| TW-26-Q3-0442 | Halloran Shelf | 21 Sep 2026 | 1,238 m | 1,412.8 | In audit | 90-day check due 20 Dec |
| TW-26-Q3-0437 | Greyling Bank | 14 Sep 2026 | 1,176 m | 986.4 | Available | Available to buy |
| TW-26-Q3-0431 | Cape Morrow | 09 Sep 2026 | 1,322 m | 1,204.6 | Retired | Halden Freight |
| TW-26-Q3-0426 | Wren Point | 02 Sep 2026 | 1,409 m | 744.1 | Retired | Pellucid Labs |
| TW-26-Q3-0418 | Halloran Shelf | 27 Aug 2026 | 1,241 m | 1,086.0 | Retired | Norrow Air |
| TW-26-Q2-0391 | Selkie Reach | 30 Jun 2026 | 1,058 m | 612.0 | Rejected | Trap data incomplete — not issued |
| TW-26-Q2-0388 | Brannock Sound | 26 Jun 2026 | 1,151 m | 530.9 | Retired | Ostra Coffee Roasters |
| TW-26-Q2-0380 | Greyling Bank | 19 Jun 2026 | 1,183 m | 1,318.2 | Retired | Kestrel Cloud |
(04)160 mThe shelf
Seven farms, each a day’s sail from a kilometre of water.
Farms sit in sheltered shallows. Sink sites sit past the 1,000 m line, where cold and pressure do the storing. Hover or tab through a site for its numbers.
(05)320 mThe twilight zone
We sink more than we sell. On purpose.
Measurements have error bars, so we subtract them. Each quarter we issue about 18% fewer tonnes than our sensors record reaching the floor. The gap covers uncertainty, leakage and a permanence buffer that sits untouched in the registry.
- ±6.8%Measurement uncertainty per batch, 95% confidence
- 1 in 20Bales carry an acoustic tag to the floor
- 365 dSeafloor re-check on every sink site, every year
Sunk vs issued, per quarter
Thousand tonnes CO₂ · Q1 2024 – Q3 2026 (to date)
Hover, drag or use ← → to read a quarter. Raw data is in the registry export.
How a tonne gets issued
Methodology v2.3, published in full. Five checks, in order. Fail one and the batch waits — or gets rejected in public.
Drone multispectral flights and diver transects every fortnight estimate standing biomass. Carbon content is measured in the lab from frond samples — never assumed from a textbook value.
One bale in twenty carries an acoustic tag. We log sink rate, drift and landing depth. Untagged bales are modelled from their tagged neighbours — and discounted for being modelled.
Seafloor cameras and sediment cores at 90 and 365 days show how much carbon stays and how much breaks down. Anything that remineralises is subtracted from the batch, retroactively if needed.
Before issuing, we deduct measurement uncertainty, a leakage estimate for nutrients the kelp took from other life, and a 10% permanence buffer that is never sold.
Every batch is verified by Meridian Assurance, an independent auditor we don’t own or advise. The raw sensor data goes into the public registry the same day it’s signed off.
(06)480 mCompany we keep
They bought tonnes, not promises.
Every retirement is published with the buyer’s name, the batch and the date. No anonymous offsetting. No “carbon neutral” badges — we don’t hand them out.
(07)640 mYour tonnes
How much do you need to remove?
Start with your residual emissions — what’s left after you’ve cut what you can. We’d rather you bought fewer tonnes than bought them instead of cutting.
Prices include MRV, third-party audit and registry retirement in your name. Tonnes are delivered only after they’re issued — you never pay for a forecast.
Estimated total
$712,500
$285 per tonne · 4 quarterly tranches from Q1 2027
- ≈ 2,604 economy return flights across the Atlantic
- ≈ 543 years of driving an average petrol car
- ≈ 129 hectares of our kelp, grown and sunk for a year
Where each dollar goes
(08)820 mThe science panel
“I’ve spent twenty years telling companies their carbon maths didn’t add up. Tidewater is the first that paid me to try harder to break theirs. I’m still trying.”
The panel is paid by a trust we can’t touch. It has published three critiques of our method. We changed the method all three times.
(09)940 mSoundings
The Sounding, once a quarter.
The full registry export, every rejected batch, and one thing we got wrong. About 1,200 words. No cheerleading.