Hold the Line

AI-verified maritime baselines for a rising Pacific

Jessica PollockSituation 2026

90 seconds on the problem, and what Hold the Line does about it.

Helping Pacific islands keep proof of where their coast used to be

As seas rise, the coastlines that Pacific nations' ocean borders are measured from are quietly changing. Hold the Line turns satellites and tide records into an ongoing, corroborated record of that coastline — built before anyone needs to prove it in a dispute.

Prototype view of the registry reading a coastal transect: change since 1984, mean rate of movement, cross-source agreement, and readings sealed and chained.

Prototype view — illustrative readings for one transect, not yet a measured record.

First, the basics

1

Sea levels are rising, and low-lying Pacific islands are seeing their coastlines erode, shift, and in places disappear.

2

Every coastal country's "maritime baseline" — the line its whole ocean border is measured from — was mapped once, using the coast as it stood at that time.

3

That border decides who can fish there — and increasingly, who can mine the seabed there — often worth far more than the tiny strip of land it's drawn from.

4

The original line still counts by law. But if it's ever challenged, it isn't decided by pointing at an old map — it's decided by proof of what the coast actually looked like.

So the Pacific is losing two things at once: land, to climate change — and sea, to the law, because the proof behind these borders has never been kept.

Small nations, enormous oceans

Tuvalu and Kiribati are tiny by land. Their ocean territory tells a completely different story.

Tuvalu

≈ the size of New South Wales Ocean territory, against just 26 km² of land — about the size of the Sydney CBD.

Kiribati

3.4 million km² — bigger than India Ocean territory, against just 811 km² of land — about the size of Canberra.

That ocean territory isn't abstract — it pays the bills.

A$39.0m a year from fishing licences — the largest single line in Tuvalu's national budget

It funds health clinics, teachers, and the boats that connect the islands — all resting on where a line was drawn along a coast that keeps changing.

A deposit is a claim. It isn't proof.

In 2012, Tuvalu lodged its baseline coordinates — deposited with the UN in 2013. Pacific states have done the same. In 2025 the International Court of Justice confirmed a country doesn't have to keep updating that deposit as its coast erodes.

That sounds like the problem is solved. It isn't — because if the line is ever challenged, a tribunal doesn't decide it on the deposit itself. It decides it on the facts behind it. The state with the better evidence wins.

It's already happened to another country

Colombia once claimed thirty-four small islands, backed by an expert survey. The other side in the dispute didn't even attack the survey — just the tidal model behind it. Colombia couldn't defend the method, and lost thirty-three of the thirty-four.

The stakes keep rising: Kiribati and the Cook Islands are already looking to license seabed mining in these same waters. The line no longer decides only who fishes — it decides who mines, and under whose law.

What goes into the record

No single satellite image is good enough to stand as evidence on its own — corroboration is what makes it proof. So the registry pulls together several independent sources for every reading.

Satellite imagery

Where the waterline actually sits, checked every five days.

Historical aerial survey

What was there decades before any dispute begins.

Nautical charts

The surveyed reef edge and low-water line.

GNSS benchmarks

Anchors every reading to a fixed, stated location.

Satellite altimetry

Elevation of each feature, measured from orbit.

How the AI actually works

The AI isn't decoration on top of a satellite feed — it's what turns raw images into something a tribunal would accept. Here's the pipeline, end to end:

  1. A computer vision model reads each image. Every new satellite pass is scanned automatically to trace exactly where the water meets the land.
  2. It cross-references that reading against tide gauges, nautical charts and historical surveys — the independent sources above — and flags anything that doesn't line up.
  3. It classifies each feature. Legally, what matters isn't just "is there land" — it's whether that land counts as an island, a rock, or something that only shows at low tide. The model makes that call from the imagery.
  4. A person checks anything contested. Flagged or ambiguous readings go to a human reviewer before they ever enter the record — the AI doesn't get the final word.
  5. The reading is sealed. Once confirmed, it's dated and cryptographically linked to the reading before it, so the record can't be quietly edited later.
  6. An AI drafts the write-up. A language model turns the sealed data into a written record in the format a tribunal — like the ICJ or ITLOS — would actually recognise as evidence.

So if anyone ever questions where the line should be, the country doesn't have to argue from memory. It can produce the record.