How to Plan a Dive: Start With the Exit, Not the Dive

Ask most divers about their plan and you'll hear about the dive.

"We're going to the canyon wall." "We want to find the octopus." "Thirty minutes, maybe forty."

That's not a plan. That's a wish list.

Here's what we ask first: how are we getting out?

What does "plan for the exit" mean?

It means you plan the dive backward.

Most divers start with what they want to do, then check whether they have enough gas to do it. We start at the other end. Before anyone talks about the reef, the wreck or the cave, the team agrees on how it gets home. With no problems. And with the worst problem, at the worst place, at the worst time.

Only then do we talk about the dive. And the dive is simply whatever fits inside the exit.

That sounds like a small change in order. It isn't. It changes every number you carry underwater.

Why do most divers plan it the other way?

Because the dive is the fun part. Nobody books a boat to practice an ascent.

And on most dives, nothing goes wrong. You swim around, you get low on gas, you come up. So the exit feels like an afterthought, something that takes care of itself.

Let's be honest. It takes care of itself right up until it doesn't. An out-of-gas teammate at the deepest point. A free-flow at the far end of the wreck. A current that wasn't there on the way out. That's when you find out whether your exit was a plan or an assumption.

How do you plan a dive from the exit back?

Five questions, in this order.

1. Where and how do we get out? The beach and the route back to it. The anchor line or the live-boat pickup. The upline. In a cave, the way out is the way in.
2. Where's the worst place to have a problem? Usually the deepest point at the end of the dive, when you've used the most gas and have the farthest to go.
3. How much gas does the exit take from there? That's rock bottom: enough for two divers breathing one supply at a stressed rate, with time to solve the problem and the full ascent.
4. How long does the exit take? The ascent is part of the exit, not the end of the dive. On a no-stop dive, that's your Min Deco ascent. On a decompression dive, it's your decompression.
5. When do we turn? Usable gas is everything above rock bottom. All usable, halves or thirds, depending on how the dive ends. That's your turn pressure. See Gas Management for Recreational Divers.

Now plan the dive. Depth, route, time, what you want to see. All of it lives inside the limits the exit just set.

Does this apply to every kind of dive?

Every one. The exit changes. The order doesn't.

• A reef or shore dive. The exit is the swim back and a direct ascent. Rock bottom and the turn pressure come first. The route is planned so you're never farther from the exit than your gas allows.
• A wreck. The exit is the upline or the anchor line, not just "up." Know where it is from every part of the wreck, and plan rock bottom from the farthest point.
• A cave. The exit is the same line you came in on, often against flow, often in silt you kicked up. Turn points are planned in volume for the most limiting diver, never one diver's psi. See The Rule of Thirds.
• A technical dive. The exit includes decompression and every gas switch. Rock bottom gets you to the next gas source, not the surface. Lose a deco bottle and the exit still has to work.

Same question every time. How do we get out?

Why do rock bottom and ratio deco matter so much?

Because they're exit tools. That's the whole point of them.

Rock bottom is the gas for the exit. It's calculated from the worst case, set aside before the dive starts, and never spent on the dive. When you reach it, the dive is over. No negotiation.

Ratio deco is the time for the exit. On a decompression dive, the ascent is the longest part of the exit, and it changes every time the dive changes. Stay five minutes longer. Go a little deeper. A computer recalculates for one diver. Ratio deco lets the whole team recalculate the exit in their heads, together, at depth. So the exit is always known, and everyone knows the same one.

That's also why we run computers in gauge mode. The exit lives in the team's heads. The instruments confirm it.

Here's the reality check.

The comfortable belief: if something goes wrong, we'll figure it out.

The truth: at the worst moment, you won't figure much out. You'll do what you already planned. If the exit wasn't planned, you'll be improvising with half your gas, a teammate in trouble and no time to think.

How do you start doing this?

On your next dive, change the order of your briefing.

• Start with the exit. Before the site, the route or the critters, say how the team gets out.
• Set rock bottom and the turn first. Use the gas planner to check your math, then run the numbers yourself.
• Say the ascent out loud. Where it starts, how fast, where the stops are, who leads it.
• Then plan the dive. And notice how much easier the dive gets when the exit is already settled.

So, on your last dive: did you know how you'd get out before you knew what you'd see?

If you want to build this into every dive you do, exit planning, rock bottom and team gas management sit at the core of Essentials of Tech.