Twenty minutes ashore, gigabytes saved at sea.
Most satellite data isn't spent by people - it's spent by devices doing things nobody asked for that day: photo backups, app updates, game launchers, cloud sync. All of it can wait for port. These are the settings that make it wait.
The day before, on shore Wi-Fi
Anything you update ashore won't try to update itself mid-passage.
- Update everything now - phone OS, apps, laptop OS, chart apps. An update you skip ashore becomes a 2 GB surprise at sea.
- Download the entertainment - playlists, podcasts, shows, books. Streaming offshore is the most expensive way ever invented to watch a sitcom.
- Download offline charts and maps for the passage and ports - Navionics regions, Google Maps offline areas.
- Let cloud backups finish - photos, iCloud/Google backup, file sync - then pause them (below) so they don't resume offshore.
Every phone aboard - iPhone
One crew phone left on defaults can quietly eat a day of plan. The boat's Wi-Fi feels like home Wi-Fi to the phone, so tell it otherwise.
- Low Data Mode on the boat's Wi-Fi - the single highest-value toggle.Settings → Wi-Fi → tap the boat network's ⓘ → Low Data Mode
- Automatic app updates off.Settings → App Store → App Updates off
- Pause iCloud Photos upload while aboard.Settings → your name → iCloud → Photos → pause / disable upload
- Background App Refresh off.Settings → General → Background App Refresh
Every phone aboard - Android
- Mark the boat's Wi-Fi as metered - makes the whole OS treat it as precious.Settings → Network & internet → the boat network → Metered / "Treat as metered"
- Data Saver on.Settings → Network & internet → Data Saver
- Play Store auto-updates off (or "unmetered only" - metered flag above then covers the boat).Play Store → profile → Settings → Network preferences
- Google Photos backup off or unmetered-only.Photos → profile → Backup settings
WhatsApp - worth its own section
It's how crews talk to home, and its defaults assume data is free.
- Media auto-download off - including on Wi-Fi. The boat's Wi-Fi is the satellite.Settings → Storage and data → Media auto-download → set all to "Never" (or remove the Wi-Fi tick)
- "Use less data for calls" on.Settings → Storage and data
- Voice notes over video calls when the link is precious - roughly a tenth of the data per minute.
Laptops - the silent heavyweights
- Windows: set the boat's Wi-Fi as a metered connection, and pause OneDrive/Dropbox sync.Settings → Network & internet → the network → Metered connection
- macOS: turn off automatic updates and pause iCloud Drive sync while aboard.System Settings → General → Software Update → ⓘ; iCloud Drive → pause
- Quit game launchers and creative-suite updaters - Steam, Epic, Adobe. They pull multi-gigabyte updates without asking.
What actually burns the data
Typical figures - they vary, but the proportions don't. Notice where the things you actually need offshore sit.
| Activity | Typical data |
|---|---|
| Weather GRIB file for a passage | 1–20 MB |
| Text messages & email home, per day | < 50 MB |
| Voice call, per hour | ~30–60 MB |
| Social feed with video autoplay, per hour | 200–500 MB |
| Video call, per hour | 300–700 MB |
| Cloud photo backup after a day of photos/video | 0.5–2 GB |
| One skipped OS or app update, catching up at sea | 0.5–3 GB |
| HD streaming, per hour | 1–3 GB |
Underway
- One device downloads weather, everyone shares it - not four phones pulling the same GRIBs.
- Save the big stuff for port - updates, backups, uploads. Make it a crew rule, not a hope.
- Check usage after each leg (Starlink app or router stats) - you can't manage what nobody measures.
This checklist exists because we're researching where offshore data really goes. If you sail with a satellite link, your numbers would help:
Take the 3-minute offshore data surveyCompiled by Molsa - an application-aware data layer for satellite-connected vessels, in development. Print this page and pin it by the nav station; your crew will find the boxes strangely satisfying to tick.