Vietnamese Swimming and the Data Gap Ahead of the SEA Games Cycle

In 2026, when I began writing about swimming for Thanh Niên Báo, archiving a national record was simple: write it by hand in a notebook — date, athlete's name, mark — and put it in a drawer. Fifteen years later I still run into that same archiving habit at youth meets, except the notebook has been replaced by a screenshot of the scoreboard forwarded through a group chat.

There is nothing administratively wrong with that. It only means we are running a sport capable of measuring to the hundredth of a second with tools that measure nothing. Within a SEA Games cycle, the cost is not this year's medal. The cost is that we do not know where our progress came from, and therefore do not know what to repeat.

A sport measured by a clock, managed by memory

Swimming is one of the few sports where the final result is already an absolute number. No line calls, no disallowed goals, no expected-goals model needed to explain anything. If an athlete touches the wall in 1:58.42, it is 1:58.42.

Precisely because the result is so clean, swimming analysis in Vietnam usually stops right there. The final time is the only thing recorded systematically. Everything that produces the final time — reaction off the blocks, the underwater phase after the dive, how the first 50 metres and the last 50 metres are paced, stroke rate, distance per stroke — mostly stays in the pool.

I once worked in the data-analysis room of a V.League club, where every training session was captured by GPS and every player had a personal load profile. Coming back to swimming, the distance between the two worlds stunned me. A mid-table V.League footballer can have his high-intensity running, accelerations and heart rate measured half by half. A swimmer who has qualified for the SEA Games may not have a single complete 50-metre split sheet on file.

Nguyễn Thị Ánh Viên was the centre of Vietnamese swimming through the 2010s, with a stack of SEA Games gold medals and two Olympic appearances. Nguyễn Huy Hoàng followed in the 800m and 1500m freestyle, competing at Tokyo 2026 and Paris 2026. Both belong to the most heavily measured group of swimmers in the country's history — and even for them, most of the 50-metre split data sits scattered across competition result files, never assembled into a comparable profile.

The SEA Games cycle makes this more urgent — not because the meet is harsher, but because it is the only yardstick the Vietnamese public actually follows. After every Games we get a medal table. We do not get a data table.

What is lost when only the final time is recorded

Take the 1500m freestyle. The final time does not tell you whether the swimmer went out too fast over the first 400 metres. It does not tell you whether the last 100 metres was a collapse or a controlled acceleration. Two swimmers can finish in 15:30 with completely different physiological stories. One has hit a ceiling. The other is two months away from a breakthrough — if the coach can read the split pattern.

Split data is not a minor detail; it is the only part that explains why a final time looks the way it does.

Without split data, coaching decisions become guesswork wearing the coat of experience. Experience is precious, but it is not reproducible. A good coach can watch a swimmer and say, you faded at the 800. He is usually right. But usually right does not appear in the report sent to the federation, and it is not passed on to his successor.

Measuring this does not require a football-grade GPS budget. It requires a protocol. Modern automatic timing already records 50-metre splits through the touchpads in the wall — the data exists, it is simply not exported, not stored, and not entered into any long-term record. Add one underwater camera and one person who can count stroke rate, and you have a technical profile good enough to compare across training camps.

This is where the football lesson earns its keep. Croatia 2026 was not a miracle — it was xG written into history. That team reached the World Cup final with 5.3 xG across the knockout rounds, while their four opponents — Denmark, Russia, England and France — combined for 7.1 xG. They scored eight goals from 5.3 xG, an overperformance of 51%. Read through the league table, it is a fairy tale. Read through granular data, it is a set of events that can be taken apart link by link.

Vietnamese swimming sits in the opposite position. We have the medal table — the result half — but we are missing the equivalent process half. Nobody can say why a swimmer broke a national record, beyond saying he swam faster.

What I said, and what I had to verify

In 2026, after the Qatar World Cup, a V.League club asked me to consult on its transfer window. They wanted to sign a foreign striker from the Thai League for USD 500,000. I analysed 19 of his matches: he had scored 18 goals but produced only 11.2 xG, a conversion rate of 31.4%, nearly double the league average of 15–18%. Seventy per cent of his goals came from set pieces. I recommended against the signing. The leadership overruled me, arguing that numbers could not replace an eye for people.

The player scored four goals in 20 matches and suffered two hamstring injuries.

I retell that story not to congratulate myself. It points to something more important: the value of data is not that it is right, but that it forces people to state clearly what they believe and why. A small GPS deviation was enough to teach me: verification is everything. In 2026 I miscalculated a striker's sprint distance — logging 1.2km instead of 0.8km — and a male colleague dismissed me with prejudice. I spent three months re-auditing 14,000 data samples and found three more systemic errors in the synchronisation software. From then on, cross-checking became the club's internal standard.

Swimming does not need a data revolution. It needs a similar cross-checking protocol, applied to numbers that already exist.

The counter-intuitive angle: a database does not produce medals

Here I have to argue against myself. There is a hidden assumption running through everything above: that if we measure more, we will swim faster. That has not been proven.

Historically, plenty of countries with sophisticated sports-data systems have failed to produce elite swimmers. Conversely, some strong swimming nations in the region operate with very manual methods and still win medals consistently. Data is an enabling condition, not a cause. Correlation is not causation, and a beautiful database does not automatically turn into a final.

The remaining risk is data theatre: buying software, building dashboards, then using them to justify what you had already decided. I have seen it in football. When a model becomes a tool for defending a position rather than a tool for asking questions, it is worse than having no model, because it dresses a guess in the appearance of precision.

In swimming this risk has a concrete shape. If a federation builds a split-archive system but uses it only to confirm what the coaching staff already believes, the output will be longer reports rather than faster swimmers. If the data is used to answer questions nobody wants to ask — why this swimmer plateaued at 19, why an athlete's best event has shifted — then it is worth something.

I believe in numbers, but only after they have passed three rounds of checking. For Vietnamese swimming, the first round has not even begun.

The signal to watch in the next cycle

In the coming SEA Games cycle, I will not look first at the medal table. What I will look for is a publicly available split-data archive for middle- and long-distance events, a personal technical profile updated across four years rather than only during competition week, and a coach willing to say in public where his swimmer stands compared with himself two years ago.

Data does not tell stories; it records everything so that I can tell them. If, four years from now, Vietnamese swimming still keeps only the medals and lets the rest drift away with the pool water, we will celebrate again without learning anything.