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The mystery of the deep is entrancing to divers. The endless blue of the ocean calls out and invites you to explore. But soon after starting scuba diving, you discover limits even on the technology that lets you breathe underwater. The need for decompression stops, which protect you from developing nitrogen bubbles in your body, limit how deep you can go. But how deep can you go without needing them?
As a diver, I’ve wondered this myself. PADI courses limit you to certain depths based on experience, and for recreational divers, you’ll probably never get close to needing a decompression stop. But where is the cutoff before you need decompression stops, and what can you do to keep from needing one? We take a look at just how deep you can go.
Importance of Decompression Stops
Decompression stops are a core part of diving, and anyone who dives needs to know how to make one. Decompression is the process of de-gassing after a long or deep dive and venting off the nitrogen that has built up in your bloodstream. These nitrogen bubbles, which are compressed at depth, run the risk of expanding in your blood as you ascend. Most recreational divers will not have to make these sorts of stops, especially if they plan their dives correctly. A single tank recreational dive should never require a decompression stop. But, in the case of an emergency, every diver needs to know how to safely ascend when they exceed their no-decompression limit or NDL.
While talking about how deep you can dive without needing decompression stops, it’s important to mention the safety stop. A safety stop is a rest for 3 minutes at 15 feet of depth. This gives you a chance to work out some of the nitrogen in your bloodstream, even if you have gone on a relatively shallow dive. The safety stop is standard practice. Every dive should include one, just for good measure, and certain recreational dives require them. For the purposes of this article, a safety stop is not the same thing as a decompression stop.
Decompression illness (DCI) is one of the greatest threats of scuba diving, and the whole point of both decompression stops and safety stops. Water exerts much higher pressure on your body than air, so much so that approximately 30 feet of water presses on you as much as Earth’s entire atmosphere does at sea level. This also works on whatever gas you are breathing and forces nitrogen bubbles into your bloodstream. At depth, these bubbles are small. When you ascend too quickly, the bubbles expand. This results in rashes, joint pain, shortness of breath, and worse symptoms, which can lead to death in severe cases.
You can recognize decompression illness through the presence of a rash, disorientation, and joint pain. If you or your dive buddy exhibit any of these, it’s important to seek help immediately. Even if it’s ultimately a mild case of DCI, the condition presents risks that are too great to ignore. DCI can be prevented by general safe diving practices, which are taught in any beginner scuba course. Don’t go too deep or exceed your NDL, and don’t ascend at a rate faster than an absolute maximum of 60 feet every minute. Running out of air can make this worse, as you may shoot to the surface to find air, or just have too little to properly decompress. We’ll cover these in more detail soon.
The safety stop
Like previously mentioned, the safety stop is meant to slowly and safely expel gas from a diver’s body as they ascend. It works much the same way as decompression stops do, only they can be done at the end of a no-decompression recreational dive. After a dive in which you have not exceeded your NDL, ascend at a safe speed to a depth of around 15 feet. Remain at that depth for three minutes. It is a chance to off-gas and is a required step for dives which last certain lengths at certain depths. The PADI Recreational Dive Planner (RDP) helps you determine when you need a safety stop. However, current best practice dictates a safety stop for every dive.
Now, your dive computer will remind you to do a safety stop at the end of every dive. It will give you a timer to make sure you off-gas for the right length. Following the tradition of a safety stop is the concept of a “deep stop.” Deep stops are not officially defined but are usually a short stop at half of your maximum depth to off-gas. These are not as widely accepted or used as safety stops. If you have one, you should trust your computer’s decompression algorithm as to whether or not a deep stop is necessary. For most divers staying within their NDL limits, a deep stop is unnecessary. However, there is anecdotal evidence to suggest that deep stops help you feel better after a deeper dive.
When to Dive Without Decompression Stops
For recreational diving, you should always be focusing on how to dive without decompression. If you’re only carrying one tank at around 200 bar, it’s dangerous to dive for too long, as you probably won’t have enough air to safely decompress. Additionally, if you’re only diving on air, you’re going to have more nitrogen going into your bloodstream than if you’re using another gas mix. In short, you should never plan to dive with decompression stops unless you’ve specifically accounted for doing so.
Technical diving and other gas mixes
Of course, there are ways to go deeper and stay down longer by using different gases. You may be asking, is there a gas mix that allows you to go deeper without decompression stops? The short answer is no. Different gases may help you stay down longer, or go deeper. They do this by limiting the amount of nitrogen that builds up in your bloodstream. But there is always a payoff, and it comes at the cost of decompression. If you want to go deeper than regular air allows, you’re going to need to decompress, no matter what. This is where we get into technical diving, which is more detailed than can be fit into this article. If you’re truly interested in knowing how deep you can go on gas mixes, consider taking a course with PADI or another dive school.
How to Dive Safely Without Needing Decompression Stops
Fortunately, the entirety of PADI’s recreational courses is built around knowing how to safely dive without needing decompression stops. The best way to do this is by planning your dive, and diving your plan. This rule is one of the most important to follow in diving, apart from remembering to breathe. It keeps you from getting lost, and it keeps you from running out of air. It also gives you a path to follow, helping you stay calm in case something goes wrong.
Of course, there are many ways to plan your dive. Perhaps the most familiar is the Recreational Dive Planner. Every PADI diver has seen these tables, which let you plan multiple dives. Also available are dive computers and the electronic RDP. Dive computers often let you plan a dive ahead of time. They keep you on schedule and allow you to move among different depths without losing track of your NDL. The eRDP is another planning tool that lets you stay at different depths for a set amount of time. It can keep you from being limited by the single-depth structure of the RDP.
Single dive planning
The RDP is, at first glance, a confusing object. It’s made of three stair-stepped tables lined with white and blue. There are a lot of numbers and not a lot of direction. But actually, the tables are quite simple to use, once you understand them. The first table asks for the deepest point of your dive, on a range between 35 and 140 feet. Below each is a column, indicating the amount of time you plan to spend at this depth. The black square at the bottom indicates the maximum amount of time you can spend there. Stay down longer, and you exceed your NDL. The gray squares in each column show you the time after which a three-minute safety stop is required.
Now, for a single dive, this table is extremely simple to use. Find the depth at which you want to dive, and trace the column to where your desired bottom time is. Make sure to round up for safety’s sake. If it isn’t in a black square, you’re safe to dive without decompression stops. Always be sure to dive with a timepiece, so you don’t exceed your NDL. If you don’t plan on diving again in the same day, you’re finished. If you do, things get a little complicated.
Planning multiple dives
For a second dive, you need to know the length of your surface interval and how deep your next dive will be. On the RDP, find the bottom time on your first dive like in the above section. Then, trace it across to table two. On this table, you will find a series of times indicating your surface interval. These will tell you how much nitrogen you will off-gas while on the surface. For example, if you stay at 70 feet for 27 minutes, you will be in pressure group N. After an hour on the surface, you will be in pressure group D. Once you flip over onto the back, you can find how deep you plan to go on your next dive. The blue number gives you an adjusted bottom time for the nitrogen already in your bloodstream.
This is particularly important to diving without decompression stops. You need to know how much nitrogen is left in your body after each dive if you’re trying to dive without them. If you don’t use an RDP or a computer that tells you how long to stay on the surface, you could end up exceeding your NDL even at a relatively shallow depth.
Multi-level dive planning
Not every dive stays at one depth the whole time, followed by a controlled ascent to your safety stop, and then the surface. Most don’t, in fact. When you’re planning on spending time at various depths, you can use computers that include an algorithm for each depth. These devices recalculate your bottom time at each depth. They show you how long you can stay down according to the nitrogen already in your blood. Computers are the most convenient. They continually adjust and recalculate based on your current depth, so you always know how long you can stay down without decompression stops. Sometimes, however, a computer can fail or malfunction. In this event, make sure you have planned ahead and know how long you have at each depth.
How Deep Is It Safe to Go?
So, how deep can you dive without decompression stops? The easy, short answer is, according to PADI’s RDP, about 140 feet. But, there are some enormous caveats to this number. First, you should never dive deeper than your training allows. PADI certified Open Water divers can only dive to 60 feet, and Advanced Open Water divers can dive to 100 feet. Only trained Deep Divers can handle anything beyond that. Even these divers can only go to 140 feet for a few minutes. That’s the second caveat — the depth all depends on how long you plan to spend down there. Twenty minutes at 60 feet is a lot different than at 100.
The information here doesn’t replace actual diving ability, of course. Don’t think you can strap on a tank and dive in without having gone through a certification course. But if you’re already certified and curious about going farther, I hope this information has helped you approach your interest safely. At the end of the day, if depth is your goal, consider taking advanced courses in technical diving. As long as you’re diving on air, focus on planning a safe dive and having fun.