Vietnamese Swimming: The Gap Outside the Lane

One morning at an indoor pool, I sat in the stands with a notebook and a phone. The scoreboard showed exactly one figure per swim: the finishing time. No 50m splits. No reaction time off the blocks. No turn times. No underwater distance after the start. When the official results sheet was handed down to the media area, it repeated the same row of numbers: name, lane, final time.

I stayed two more hours, hand-timing every swim with a stopwatch, with cumulative error that could reach three-tenths of a second. For someone used to a single football match handing him more than two thousand data points, the feeling was like being given one sheet of A4 paper to describe a city. Numbers do not lie, but they know how to hide something. And here, they hid almost everything.

Context: two data worlds

At major meets — the Olympics, the World Championships, the Asian Games — organisers publish results detailed down to every 50m. You can tell whether a swimmer went out faster or slower than a rival over the first 100m, how long their rest between two turns lasted, whether their start took 0.68 or 0.74 seconds. Those numbers exist to do more than decorate a report. They are the entire architecture of a race.

At home, most national and junior meets publish only final times. Nothing about that breaks any rule. But it creates a gap that anyone doing analysis has to fill by hand-timing from the stands — and hand-timing from the stands only gives you your own number, never the number of a whole generation.

I began my career at a sports newsroom as a swimming reporter. Back then I thought this job was about observation. Later, when I moved into sports data analysis, I understood: observation without a record is only memory, and memory does not add up. The SEA Games 31 held in Hanoi in May 2026 was the last time I saw a domestic meet with enough resources to do that job properly — and even then, the detailed split sheets were never archived publicly once the event closed.

Core: the chain of evidence

There is a very simple question our results sheets currently cannot answer: two swimmers both go 1 minute 52 seconds in the 200m freestyle — which of them has the higher ceiling?

The only way to answer is to cut the distance in half. The first goes out in 54 seconds over the first 100m and fades home. The second goes out in 56 seconds and accelerates over the last 50m. Two completely different spreadsheets. One is near his speed limit; the other still has untapped physical headroom. If all you have is one number, you will treat them the same way — and that is the most expensive mistake in youth development. A split time is not a number. It is a confession.

The same holds for the 100m. The start and the underwater phase account for a large share of the final time, but that share shifts from swimmer to swimmer: some dominate the first 15m, others live on stroke rate over the closing 50m. Without splits, there is no way to tell them apart. That summer in Saigon, I learned that data also needs watering. Without it, data dies on some coach's hard drive, or in a spreadsheet nobody opens again.

And there is another layer few people discuss: the consequences of missing data do not stop at the technical level. They push the public towards sentiment. When nobody publishes splits, the debate about a young talent is driven by feeling: people remember a spectacular finish, and forget that the swimmer's opening 100m was nearly two seconds off the regional benchmark.

In the betting and valuation market, that gap turns into an invisible discount. Bookmakers cannot price what they cannot measure — so they price with a safety margin. Which means our swimmers always enter a comparison carrying a pre-loaded handicap. That handicap comes from the silence of data, not from their speed.

Every lane is a data point, but not every data point gets recorded as a lane.

Contrarian angle: data is not the bottleneck

This is where I want to argue against myself.

Suppose tomorrow morning every domestic meet suddenly published complete split sheets. I do not believe the sport would change within three years. The bottleneck lies elsewhere, and data is only its symptom — infrastructure and competition calendar.

A country with only a handful of 50m pools, and with long-course meets countable on one hand each year, has a problem that is not about what we measure. The problem is how few chances we get to measure. Long-course and short-course swimming are two different sports. Without a dense long-course calendar, swimmers unconsciously train for the short course — and every beautiful technical metric on paper fails to convert into results at continental level.

There is a subtler trap too: publishing data early can backfire. When a 15-year-old's splits go online, pressure to optimise the visible number appears. Coaches start designing training to make the opening 50m prettier, instead of making the physical base bigger. Correlation is not causation. A swimmer with a fast opening 50m will not necessarily have a better 200m — in many cases, the opposite is true.

So I am not calling for a data revolution. I am calling for a record that is kept.

What to watch

The signal worth tracking over the next two years is not a new national record. It is whether one domestic meet publishes a full split sheet, archives it publicly, and keeps doing so for at least three consecutive editions. Publishing once is news. Publishing three times running is a system.

If that happens, watch the next step: the number of junior swimmers with a recorded technical profile will rise, and the share of talents misjudged will fall. If it does not happen, we will keep arguing about talent from memory.

And memory, as I learned, does not add up.