Modes explained

Gauge Mode on a Dive Computer: What It Does and Who Should Use It

Scroll through the mode menu on almost any dive computer and you'll find Gauge, sometimes called Bottom Timer or Depth Gauge mode. It turns a computer into an electronic depth gauge and stopwatch. For a small group of trained divers it's exactly what they want. For most recreational divers it's a mode to understand and then leave alone.

This guide explains what gauge mode changes, who uses it on purpose, why many computers restrict switching back afterwards, and what to check before you buy a computer for its gauge features.

What gauge mode actually does

In its normal modes, a dive computer reads depth and time, runs those through its decompression model and shows you things like no-decompression time, ceiling or stop information, and ascent warnings. In gauge mode it still reads depth and time, but it stops showing decompression guidance.

What you typically see instead:

• Current depth and maximum depth
• Dive run time, often with a resettable stopwatch
• Average depth, on many models, which is useful for people working from tables or plans
• Water temperature
• Ascent rate information on some models

Some computers keep a few warnings active in gauge mode, while others remove most of them. Exactly what stays on screen varies by brand and model, so the manual is the only reliable source.

Who uses gauge mode on purpose?

The common thread: each of these divers has another trained, deliberate way of managing decompression. Gauge mode is a tool inside that system, not a replacement for one.

Why switching back is often restricted

This is the part that surprises people. Many dive computers will not let you go straight from gauge mode back into air or nitrox mode after a dive. Some impose a waiting period; others require a period with no diving before the decompression mode becomes available again.

The reason is simple. While you were in gauge mode the computer wasn't tracking your tissue loading in the way its normal modes need. If it let you switch back immediately, it would start calculating as if you had a clean slate, which could badly understate the nitrogen you are actually carrying. Restricting the switch prevents that mismatch.

Gauge mode vs a dedicated bottom timer

If what you really want is an independent depth and time reference, consider whether a separate device suits you better than switching your main computer's mode.

For most recreational divers, keeping your main computer in its normal mode and carrying a simple backup gives you more information, not less. Our guide to a backup depth gauge and timer kit covers that setup in detail.

Browse digital bottom timers Shop depth gauges

Gauge mode on rental and shared computers

Rental computers deserve special mention. A dive center's fleet of computers is used by many people, and the shop has a system for tracking which unit was used by whom and when. If you change the mode on a rental computer, you can disrupt that system. The next renter might pick up a unit that won't enter normal mode, or a unit whose memory of recent dives no longer matches the person wearing it.

The same applies to a computer shared within a family or between buddies. A computer tracks one body's tissue loading. Swapping it between people during a trip already breaks that assumption, and adding mode changes on top makes the history even harder to interpret. Each diver should wear their own computer for the whole trip, in the mode the dive shop or their training expects.

If you are trained to dive in gauge mode and want to use it on a rental, tell the shop before the trip so they can give you a unit set up for it, or bring your own.

Common gauge mode mistakes

1. Switching modes on a rental or borrowed computer. You may not know its recent history, and you may lock the next user out of normal mode. Ask the dive shop first.
2. Selecting gauge by accident. On some computers the mode menu is a couple of button presses from the main screen. Confirm the mode on your pre-dive check every day.
3. Assuming gauge mode is "more advanced". It's simpler, not more capable. It removes guidance rather than adding it.
4. Using it without the training to plan dives independently. Gauge mode assumes you know how to manage your dive another way. If you weren't trained to, don't use it.
5. Forgetting about the lock period before a trip. If you've used gauge mode recently, check whether your computer will allow normal mode on day one of your trip.

What to check if you're buying for gauge features

If you're trained to use gauge mode and it matters to your purchase, look at these points in the manual before you buy:

• Does it show average depth, and can you reset it during the dive?
• Is there a stopwatch you can start and reset underwater with gloves on?
• Which warnings stay active in gauge mode?
• How does the computer handle switching back, and for how long is it restricted?
• Is the gauge-mode display large and readable, or is it a cramped secondary screen?
• Does the logbook and app record gauge dives clearly so you can tell them apart later?

If you only want depth and time as a backup, a simple bottom timer may be the cheaper and cleaner choice. If you want a second full computer, see our guide to backup dive computers.

Browse backup dive computers