Aqualung i300C Wrist Dive Computer Black/Blue

Aqualung i300C Wrist Computer: Entry-Level Recreational Dive Computer with Bluetooth Logging

The Aqualung i300C is a wrist-worn dive computer built for recreational divers who want straightforward, reliable dive tracking without a complicated setup or a steep learning curve.

This listing is for a used unit, so the condition matters. Read the seller's notes carefully before buying, especially regarding battery history and any signs of screen wear or seal degradation.

If you are newly certified or a few years into recreational diving and want a personal computer you can pick up and use without much fuss, the i300C is worth a serious look.

What It Does Underwater

The i300C runs on a Bühlmann ZHL-16C-based PZ+ algorithm to calculate your no-decompression limits. That means it tracks how much nitrogen your body is absorbing at depth and tells you how long you can stay before you need to make a decompression stop. For recreational diving, this is the core job, and the i300C handles it across all standard conditions.

It supports four operating modes:

• Air tracks your dive on standard compressed air, displaying depth, time, and no-decompression limits.
• Nitrox lets you dive on enriched air mixtures, with support for up to three nitrox mixes and 100% oxygen. This covers everything from a standard 32% EAN mix up to pure oxygen used in surface intervals or specialized situations.
• Gauge turns the computer into a depth gauge and run timer, useful if you want to follow a pre-planned profile or dive with a separate decompression table.
• Free Dive tracks depth and surface intervals for breath-hold diving. Importantly, the i300C lets you switch between scuba and freedive modes on the same day without losing your nitrogen calculations, which is a practical detail if you mix both in a single outing.

Maximum depth readout is 330 feet (100 meters), well beyond the recreational limit of 130 feet. Altitude adjustment works up to 14,000 feet (4,270 meters), so it compensates automatically if you are diving a mountain lake.

Ease of Use in Practice

One of the more thoughtful design choices is the water-activated on switch. The computer wakes up when it hits the water, so there is nothing to press or remember at the surface. That removes one small source of pre-dive stress.

A pre-dive planning feature lets you preview your next dive before you get in, so you can check your no-decompression limits at a target depth without committing to a full dive.

The backlight makes the display readable in low light, and there are both audible alarms and a high-visibility LED warning light for safety alerts. You get the alert through sound and through sight, which matters when ambient noise or distraction might cause you to miss one or the other.

A single button gives you instant access to your last dive's maximum depth and bottom time at the surface, without navigating any menus.

Battery and Data Retention

The i300C runs on a standard 3.0V CR2450 lithium battery, which you can replace yourself. No sending it to a service center. When you swap the battery, the computer retains all your settings and nitrogen calculations, so a battery change mid-trip does not wipe out your dive data or reset your decompression state.

Because this is a used unit, it is worth asking the seller how old the current battery is and whether the battery compartment seal has been inspected recently.

Dive Log and Connectivity

The i300C stores your last 24 dives in its log, along with a history mode that tracks total number of dives, maximum depth ever reached, total dive hours, and lowest recorded temperature.

For divers who want to review full dive profiles on a computer, the i300C connects in two ways:

• Bluetooth pairs the computer wirelessly with the DiverLog app for quick log transfer and sharing.
• Download cable (sold separately, SKU: UDRPCI200) connects it to DiverLog software on Mac or PC for full profile viewing, settings control, notes, and photo or video storage. DiverLog itself is also purchased separately at ediverlog.com.

The software connection also allows user-updatable firmware, so the computer can receive feature updates if Aqualung releases them.

What Comes in the Box

• Digital instruction manual
• Safety reference information
• DiverLog brochure
• Quick reference card
• Lens protector
• Battery compartment opening tool

No download cable is included. If you plan to use the desktop software, budget for that separately.

Who This Is Not For

The i300C is not air-integrated, meaning it does not connect to a transmitter on your first stage to display your tank pressure. If that is something you want, you would need a different computer.

The 24-dive log is also relatively compact. If you dive frequently and want a long on-board history without regularly offloading to a phone or computer, that limit will come up sooner than you might expect.

Technical divers or those running complex multi-gas decompression profiles will find the i300C too limited for their needs. It is built for recreational diving, and that is where it performs well.

The Honest Summary

The i300C is a clean, capable recreational dive computer with a sensible feature set and no unnecessary complexity. The water-activated switch, user-replaceable battery with data retention, and four practical modes make it easy to live with on a regular basis.

Buying it used means doing your homework on condition. If the unit checks out, it gives you solid Bühlmann-based dive tracking, Bluetooth logging, and nitrox support in a straightforward package.