The Monterey Peninsula offers some of the most spectacular, albeit challenging, cold-water diving in the world. As you prepare for your PADI Open Water Diver training here, your Garmin Descent G2 will be a critical tool—not just for tracking your depth and time, but for managing the specific variables of California’s cold, kelp-filled waters. This primer cuts through the advanced technical features to focus strictly on what you need to know to pass your course and dive safely in the Pacific.
The Environment: Why Monterey is Different
Before we touch the buttons, understand the environment. Monterey Bay is nutrient-rich, which means two things: incredible marine life and variable visibility (often 10–30 feet). The water temperature hovers between 50°F and 60°F (10°C–15°C) year-round.
What this means for your computer:
- Thick Gloves: You will likely be wearing 5mm or 7mm neoprene gloves. The G2’s touchscreen is great on land, but underwater with thick gloves, it is unreliable. You must learn to navigate using the physical buttons.
- Low Light: The kelp canopy can block sunlight. You’ll need to be comfortable reading the high-contrast display and understanding the backlight settings.
Step 1: Pre-Dive Setup (Do This on Land)
Do not wait until you are bobbing in the swell to set up your computer.
1. Select "Single-Gas" Mode
For your Open Water course, you will be using standard air.
- Press the top-right START button.
- Select Single-Gas mode. This is the simplest screen layout and ensures you aren't distracted by technical diving features.
- Check your Gas: Ensure it is set to Air (21% Oxygen). If you are diving Nitrox later, this is where you’d change it, but for now, stick to Air.
2. Configure for Cold Water
- Disable Touch (Optional but Recommended): While the G2 automatically locks the touch screen during a dive, you want to rely 100% on buttons. Get used to the "Up" (Middle Left), "Down" (Bottom Left), and "Select" (Top Right) workflow.
- Backlight: Ensure your backlight brightness is high enough to see in murky water. Go to Menu > System > Backlight and set it to a level that is visible but conserves battery (e.g., 50-60%).
Step 2: The Pre-Dive Check
Your instructor will have you perform a "BWRAF" safety check. When you get to "Computer," here is your routine:
- Wrist Check: Ensure the strap is tight. Neoprene wetsuits compress as you descend, making the strap loose. The G2 comes with an extra-long strap—use it if the standard one is on the last notch over your thick wetsuit sleeve.
- GPS Lock: Before you descend, hold your wrist above the water for a moment. The G2 uses GPS to mark your entry point. Wait for the ring on the screen to turn Green. This saves your exact location, which is a cool feature to look at later on the map.
Step 3: In-Water Operation
Once you descend, the G2 automatically switches to the dive screen. Here is what you need to monitor:
The Main Screen
- NDL (No Decompression Limit): This is the most critical number. It tells you how many minutes you can stay at your current depth without needing a mandatory decompression stop. As a student, you should never let this hit zero.
- Depth & Time: Large, easy-to-read numbers. Your instructor will ask you to signal your remaining air and your depth/time frequently.
- Ascent Rate: On the side of the screen is a bar graph (color-coded green/yellow/red). If you ascend too fast, the watch will vibrate and beep aggressively. In Monterey’s low viz, you might not have a visual reference, so trust this alarm. Slow down until the vibration stops.
The Compass
- Navigation is a core skill in the Open Water course.
- You can access the compass by pressing the DOWN (bottom-left) button to scroll to the compass screen.
- To lock a heading, point the 12 o'clock position of the watch at your target and press the START button. A green deviation marker will appear to help you stay on course—invaluable when navigating through a kelp forest where landmarks are hidden.
Step 4: The Safety Stop
This is a requirement for every PADI dive.
- Automatic Trigger: When you ascend to 15 feet (5 meters), the G2 will automatically pop up a "Safety Stop" timer counting down from 3:00.
- Stay in the Zone: The text will be yellow or green if you are at the right depth. If you float up too shallow (above 10-12 feet), the timer will pause and turn red. Exhale, descend slightly, and the timer will resume.
Step 5: Post-Dive Care
Salt crystals are the enemy.
- Rinse Immediately: Monterey water is salty. As soon as you are out, submerge the watch in fresh water.
- Press the Buttons: While submerged in fresh water, press all the buttons a few times. This flushes out salt water that can crystallize and make the buttons sticky or unresponsive.
- Sync: Open the Garmin Dive App on your phone. Your dive profile, heart rate, and GPS entry/exit points will upload automatically, giving you a digital logbook to show your instructor.
Backgrounder Notes
As an expert researcher and library scientist, I have reviewed the article and identified the following key concepts and facts. These backgrounders provide technical and environmental context to help a reader better understand the complexities of cold-water diving with advanced technology.
PADI (Professional Association of Diving Instructors)
PADI is the world’s largest scuba diving training organization, providing standardized education and certification levels recognized globally. Their "Open Water Diver" course is the foundational certification that teaches the essential physics, physiology, and skills required for recreational diving.
Kelp Forests
Predominantly made of Giant Kelp and Bull Kelp, these underwater ecosystems are among the most productive on Earth, providing habitat for thousands of marine species. For divers, they create a unique "canopy" effect that can block sunlight and require specific navigation skills to avoid entanglement.
Neoprene Compression
Neoprene is a synthetic rubber containing tiny nitrogen bubbles used for thermal insulation in wetsuits; as a diver descends, the increased water pressure compresses these bubbles, making the suit thinner and less buoyant. This physical change is why a watch strap that feels tight on the surface may become loose and slide around the wrist at depth.
BWRAF (Pre-Dive Safety Check)
BWRAF is a mnemonic used by divers to perform a final equipment check with their buddy before entering the water: BCD, Weights, Releases, Air, and Final OK. It ensures that all life-support systems are functioning and that both divers are familiar with each other's gear configurations.
NDL (No Decompression Limit)
The NDL is the maximum amount of time a diver can stay at a specific depth and still ascend directly to the surface without requiring mandatory decompression stops. This limit is calculated based on the amount of nitrogen your body absorbs while under pressure.
Ascent Rate
Standard safe diving practice requires an ascent rate no faster than 30 feet (9 meters) per minute to allow absorbed nitrogen to leave the body safely. Ascending too quickly can cause nitrogen bubbles to form in the bloodstream, leading to decompression sickness (the "bends").
Nitrox (Enriched Air)
Nitrox is a breathing gas that contains a higher percentage of oxygen (usually 32% or 36%) than standard atmospheric air (21%). By reducing the percentage of nitrogen, divers can significantly extend their No Decompression Limits, allowing for longer stays at depth.
Safety Stop
A safety stop is a recommended three-minute pause at 15 feet (5 meters) during the final ascent of every dive. This pause provides an extra margin of safety, allowing the body to "off-gas" additional nitrogen before the diver reaches the surface.
Salt Crystallization
When seawater evaporates, it leaves behind abrasive salt crystals that can jam mechanical parts and degrade seals. Rinsing equipment in fresh water and manipulating buttons while submerged prevents these crystals from forming inside the delicate housing of dive computers and cameras.
Digital Dive Log
A dive log is a legal and personal record of a diver's history, tracking depth, time, and gas consumption. Modern computers like the Descent G2 automate this process by syncing with mobile apps to create detailed visual profiles of the dive's duration and location.
