Getting your dives in
Shearwater. bottomtime reads Shearwater Cloud's own database on this Mac, so there is nothing to export. Open Shearwater Cloud first and make sure it shows your latest dives, then click Read Shearwater Cloud. If Shearwater Cloud isn't on this Mac, export a database from it on another computer (File → Export → Export Database) and add the .db file.
Garmin. Sign in to Garmin Connect once. bottomtime downloads the original file of every dive your watch synced, and after that only the new ones. Dives that were uploaded to Garmin Connect from another brand's computer are skipped, because bottomtime reads those computers directly and gets more from them.
Files. Add files… takes .fit files from a Garmin and .db files exported from Shearwater Cloud.
Reading the same dives twice is harmless: bottomtime recognises dives it already has. Settings can make it look for new dives each time it opens.
The dive list
# Dives numbered in date order. Pool and test dives, shorter than 2 minutes or shallower than 2 m, aren't numbered and are hidden unless you include them.
Name The site you typed in Shearwater Cloud, or the name Garmin Connect gave the dive if it says more than "Single-Gas Dive".
Runtime From the Garmin when it logged the dive, since its clock carries the time zone. The Garmin keeps recording through short surface intervals, so its runtime can run longer than the Shearwater's.
Max depth The deepest reading from any computer on the dive.
Deco Minutes a computer showed a required stop. When two computers disagree, the longer one.
Max GF99 The highest GF99 the Shearwater showed during the dive.
GF99 surfacing The highest GF99 in the last ten minutes of the dive. It matches the end-of-dive GF99 that Shearwater Cloud calculates.
CNS The highest oxygen toxicity percentage any computer showed.
Depth gap On dives two computers logged, how far apart their depths were below 5 m, as a percentage. The dive's page says which read deeper and how much of it their water settings explain.
Computers Every computer that logged the dive.
Click a column to sort by it. The chart above the list plots any of these columns for each dive by date; pick the column with Chart, and click a dot to open that dive.
Reading a dive
Each computer gets its own colour. The solid line is depth, and the dashed line in the same colour is the deco ceiling the Shearwater calculated. Below are GF99 and ppO2 on the same time axis. Move the pointer over the charts, or use the arrow keys, to read every computer at the same moment.
No two dive computers' clocks agree. bottomtime takes the time zone from the Garmin, then slides one depth profile against the other until they match best. The seconds left over are shown under the chart. Neither log is changed, merged, or resampled.
When two computers logged the dive, How the computers compared says how far apart their depths were below 5 m, and how much of that their water density settings explain. A computer set to lighter water reads deeper: fresh water (1000 kg/m³) reads 2% deeper than EN13319 (1020). Shearwater's "salt" is 1030 kg/m³ and Garmin's is 1025. Below that, a table puts each computer's settings, required stops, and CNS side by side, with the values that differ in bold.
Terms
GF99 How close your leading tissue is to its Bühlmann limit at your current depth, as a percentage. 100 means you are at the limit.
Ceiling The shallowest depth the computer would let you ascend to right now.
@+5 What your time to surface would be if you stayed five more minutes at this depth.
TTS Time to surface, including every stop.
NDL No-decompression limit: minutes left before you'd need a stop.
CNS Your oxygen exposure as a percentage of the allowed limit.
ppO2 Partial pressure of oxygen in what you are breathing.
Your data
Everything stays on this Mac, in
Export all saves every dive as a CSV file you can open in Excel or Numbers, plus a dives.csv with one row per dive. Each dive's file has every sample from every computer, with the units in the column names. Values in exports are always metric.
bottomtime sends nothing about your dives anywhere. It contacts Garmin Connect only to download your dives, and GitHub only to check for a new version, which you can turn off in Settings.
Something wrong?
bottomtime is open source and made by one diver. Report a problem opens a page on GitHub where you can describe it.