Why I log every dive (and built a website to do it)
A paper logbook is a nice object. A database is a better one. On turning fifteen years of scribbles into something you can query.
I have kept a paper logbook since my very first open-water dive (dive #1, Bussloo, June 2005). Ink, stamps, a buddy’s signature, the occasional smear of salt water. It is a lovely object and I would grab it in a fire.
It is also almost useless as data.
The questions a logbook can’t answer
How many hours have I spent underwater? Which was my coldest dive? How many of my cave dives were on a scooter, and did the average depth of those change once I switched to sidemount? Every one of these is a five-second query against a table and a twenty-minute flip through pages — and I only ever did the twenty-minute version once.
So the log lives in a database now. Every dive is a row: number, date, site, depth, time, gas, tags, buddies, the profile from the computer, the photos, and a scan of the paper page it came from. The paper book stays the source of the story; the database is the source of the numbers.
What “every dive” means
Every dive. The training dives at 12 metres in a quarry. The one where the visibility was 50 cm and we called it after nine minutes. The ones nobody would put on Instagram. The point of a log is that it is complete; the statistics on the dive page are only honest because the boring dives are in there too.
Why a website
Because a spreadsheet is where data goes to be forgotten. Putting the log on a page with a map and a search box means I actually look at it, and because the page is public I keep it tidy. A private dive can stay private — it still counts in the totals, it just doesn’t show up in the list.
def hours_underwater(dives: list[Dive]) -> float:
return sum(d.duration_min for d in dives) / 60That’s the whole business logic. Everything else is plumbing, and plumbing is the fun part.