Offline dive logging: keeping records with no internet

Offshore, the internet is often slow, shared or missing for days. The paperwork does not wait for it. In the UK, the supervisor enters the diving operation record's particulars during the operation (regulation 10(1)(c)). Canada's rules ask divers to record each dive "as soon as possible after making a dive" (section 63(2)). So any digital tool you use at sea has to work with no connection, and has to make it obvious what has and hasn't been backed up. This guide covers how to set that up and keep it working on a vessel or platform.

What "offline-first" should mean

Many apps say they work offline. For dive records, check for these five things:

1. It saves to the device first. The record exists the moment you save it, with or without a signal.
2. It keeps working for a full rotation. Your sign-in and the features you pay for still work after weeks without a connection.
3. It shows the sync state of every record. You can see at a glance what has reached your account and what hasn't.
4. It never silently overwrites. If the same record was changed in two places, you are told, and you decide what happens.
5. It allows signatures without a network, so sign-off happens on deck, not weeks later.

Before you sail: a pre-mobilisation checklist

Do all of this while you still have a good connection, at home, in the hotel or at the heliport.

• Sync everything, so your devices and your account hold the same records.
• Sign in on every device you will use, and open the screens you will need while you are still online.
• Set up sign-off access. Give your supervisor or dive partner access to sign your dives while you both have a connection. Offline signing relies on a key each app stores in advance.
• Charge and protect the device. Use a waterproof case and pack a power bank. Follow the site's rules on phones in dive control and in hazardous areas. HSE's guidance on hazardous area classification lists electrical equipment as an ignition source and expects equipment in a hazardous area to be classified for its zone, so an ordinary phone may not be allowed there.
• Make a backup and store it off the device (see below).
• Pack your paper logbook if your scheme requires one. A digital record goes next to it, not in place of it.

In DIVEOPS PRO, the Prepare for offshore button on the dashboard does most of this in one step. It synchronises your records, refreshes your membership so paid features keep working offline for up to 30 days (never past the end of your plan or trial), saves the app screens on the device in the language you are using, including Credentials and Profile, and asks the browser to protect your data from automatic clean-up. It then lists each check with a tick or a warning. It does not download the keys used for offline sign-off, so a supervisor who will sign by QR code still needs to open Credentials once while online (see below). The same screen can create an encrypted backup file (AES-256, protected by a passphrase you choose) of everything on the device: dives, ledger, signatures, photos, projects and chamber records. Store that file somewhere else, such as a USB stick or a laptop. The passphrase cannot be recovered, so write it down somewhere safe.

Why "protect from clean-up" matters

Web apps store data in the browser. MDN's guide to storage quotas and eviction explains that this storage is "best-effort" by default. If the device runs low on space, the browser can delete a site's data, starting with the least recently used site. Data in persistent storage is only deleted if the user chooses to delete it. Chrome, Edge and Safari decide automatically whether to grant persistence; Firefox asks you. MDN also notes that Safari, with cross-site tracking prevention on, deletes script-created data for a site that has had no user interaction in the last seven days of browser use.

The practical points:

• Keep free space on your phone during a long trip.
• Open your logbook regularly, rather than once a month.
• Never treat the device as your only copy.

Working offline: what the sync states mean

Every DIVEOPS PRO dive record shows its sync state:

The dashboard also shows how many records are waiting to sync, so you can tell whether a short burst of vessel Wi-Fi has cleared the queue.

To avoid conflicts, edit each record on one device. If you log on your phone, don't edit the same dive on a tablet until both have synced.

Signatures with no signal

Sign-off is where paper usually falls behind. The supervisor rotates off and the entries never get signed. DIVEOPS PRO handles this with a QR handoff between two phones:

1. On the diver's phone, open Credentials and choose the dive. The app shows a QR code with the dive summary and a fingerprint (hash) of its exact content.
2. The supervisor scans it in their own app, checks the summary, and signs.
3. The supervisor's app shows a QR code back. The diver scans it.
4. The signature is saved on the diver's device and checked by the server the next time the diver opens Credentials with a connection. If the dive was changed after the supervisor reviewed it, the signature is not accepted.

A supervisor can also enter a dive for a diver and pass it over by QR. It reaches the diver's inbox for approval the same way, when the diver next opens Credentials online.

Four things to know before you rely on it:

• Set up access while you both have a connection, then have the supervisor open Credentials once, online, on the phone they will use. That is when their app stores the key it needs to sign or enter your dives with no signal.
• Only synced dives can be shown for signing. In the current web app, the dive must already have reached your account once, so sync whenever the vessel's connection allows.
• A QR code must reach the server within 7 days of being made. Open Credentials as soon as you get a connection; an older code is refused and the supervisor has to sign again.
• A QR signature waiting to upload is not included in the encrypted backup, so don't leave it waiting on the phone.

Practical tips for vessels and platforms

• Log straight after the dive, using dive control's times, while the details are fresh.
• Sync little and often. Vessel Wi-Fi is often shared and rationed. Small, frequent syncs get through more reliably than one big upload at the end of a hitch.
• Keep the device's date and time correct. Timestamps come from the device clock, so check it after crossing time zones.
• Finalise only when the entry is right. Finalised records are locked, so check the entry against dive control's figures first.
• Check the queue before crew change. Make sure the dashboard shows nothing waiting to sync, or make a fresh backup if it does. Check that Credentials shows no handoffs waiting to upload.
• Gas figures: the gas calculators work offline once the app screens are saved, and link to their formulas and assumptions. They are not independently validated, so verify every figure against your company's procedures.

Backups that survive a lost phone

Records have to outlast the device. In the UK, a diver keeps their daily record for at least two years after the last entry (regulation 12(3)). In the US, 29 CFR 1910.440 sets retention periods for employers' dive records. A phone dropped over the side should not take any of those records with it.

• One copy off the device, one off the vessel. For example, an encrypted backup on a USB stick in your bag, plus your synced account. A third copy at home is better still.
• Back up before you sail and at every crew change. Those are the points where devices get lost or swapped.
• Export in open formats now and then. DIVEOPS PRO exports your logbook as UDDF or a full JSON backup, and any dive as a PDF.
• Test a restore on a spare device once. In DIVEOPS PRO, restoring a backup adds missing records and never overwrites the ones already present.
• Copy your signed paper pages too, if you keep a paper logbook.

Log your next rotation offline

Start a free logbook before you mobilise, run Prepare for offshore while you still have a signal, and keep your records safe for the whole trip. See how DIVEOPS PRO works offshore, compare plans and prices, and read how supervisors handle the daily paperwork.