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Diving from a boat – advice from the experts

Joshua Shankle and his wife, Rachel offer their thoughts on diving from a boat. Both are experienced divers and sailors. They are currently mid-pacific on a world cruise

As cruisers, we can find ourselves in some of the most beautiful places this world has to offer. But more often than not, the real magic lies just below the surface, in the world of the aquatic. Diving from a boat can be a great way to get a better idea of the world that lies below your keel.

My wife, Rachel, previously worked as a research diver and Divemaster. Years ago, as we prepared to go cruising, she made it known that one of her few requirements of going sailing long term was to have her own dive compressor on board. As a result, we’ve made diving a priority during our voyage planning, and have been immensely rewarded with some of the most incredible undersea experiences of our lives.

Today scuba diving is considered a relatively safe activity due to advancements in gear, safety procedures and, above all, standardised training requirements. But it could be easy to overlook the risks inherent in the sport.

Scuba certifications ensure all participants have the same knowledge and understanding of the sport at a given certification level, and this should be the first step in diving safely from your boat.

Be careful how you lift dive gear into the dinghy. Photo: voyagesofagape.com

Before setting off on your own, it’s advisable to complete your PADI Open Water course, as well as an Advanced course. Log enough dives that you are comfortable underwater without a Divemaster to ensure you have adequate knowledge of the gear, safe diving practices, and navigating underwater.

In theory, you are ready to dive independently of a shop and Divemaster after passing your Open Water (level one course). However, to be truly confident I recommend completing an Advanced course and/or have a minimum of 15-20 dives. We all learn at different speeds and it is a unique timeline for everyone to gain confidence in the water.

Tanks and air

There are many makes and models of compressors on the market, including gas, diesel, or electric. We wanted something self-contained, and since our yacht Agápe relies entirely on solar for power, an electric model was out of the question.

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We purchased a MaxAir 35, powered by a 6hp petrol engine. This compressor uses a combination of a condensate trap and a disposable filter to purify and dry the air while filling dive tanks, usually within 18-25 minutes depending on tank size and ambient temperature.

Aluminium tanks are a popular choice. Photo: voyagesofagape.com

Not everyone will need their own compressor to go diving from a boat. In fact, unless you are an avid diver I’d recommend against it. These seemingly simple devices are one of the most crucial elements of diving safety: to ensure clean, pure, and dry air they must be well maintained and have the filters changed regularly.

In almost every diving hot spot there is a dive shop that will refill tanks for roughly US $10. If there are no dive shops in the area, listen for the sound of another yacht’s compressor running.

On Agápe, we estimate the cost of filling a dive tank to be $3-4. So, when people come by to ask if we can fill their tanks, we usually ask for $5 to cover consumables and wear and tear on the compressor. Many cruisers with a compressor on board may be willing to do the same if asked.

For tanks you have a choice of steel or aluminium. On Agápe we carry Aluminium 80s. These are by far the most common for the simple reason that they are cheaper than steel tanks.

New aluminium tanks cost around $150, whereas a steel tank is closer to $300. This cost-saving does have a few drawbacks, though. The lifespan of aluminium tanks are usually shorter than steel and they are much more buoyant. With aluminium, you’ll have to wear more weight as the tank becomes more buoyant at the end of the dive, unlike steel tanks that remain negatively buoyant.

Steel is also stronger and the tanks can be smaller, but aluminium has the advantage of being slightly more corrosion resistant.

Other gear

As for the rest of your kit, it depends on how often you intend on diving from a boat and what you personally find comfortable. I have found that streamlined, backfill BCDs (Buoyancy Control Devices) are not only cheaper but smaller and easier to store onboard.

If possible, find one with a built-in backup regulator on the inflator hose and integrated weight bags, as this will further streamline your gear.

One of the most important pieces of gear is a dependable dive computer or watch. A dive computer will constantly monitor your depth and time to calculate safe diving limits using dive tables. While it is possible to do these calculations on your own, a computer is more reliable.

Once in the water do a final check with your buddy. Photo: voyagesofagape.com

Rachel and I each dive with computers that tell us all relevant information to ensure we are diving within established dive profiles.

A good quality BCD, first stage, regulator, and computer with depth and pressure will usually cost around $850. Even more affordable scuba sets are usually good quality and if rinsed, dried, and stored out of the sun, and can last for hundreds, even thousands of dives.

To ensure that your kit is ready to go, even in the most remote places, it’s a good idea to carry an assorted O-ring set, a spare hose or two, and a replacement battery for your dive computer.

The mask and fins you usually use for snorkelling should suffice for most recreational diving, but an additional set will bring your total to around $1,000 (US) for a full set of quality gear, or roughly the same cost as 15 dives through a tour company.

Having your gear onboard also has the advantage that if you ever foul your chain or anchor, you’ll be able to untangle it yourself and maybe even give the boat’s bottom a quick scrub while you’re at it.

Diving in

Our tanks live happily secured to the mast pulpit where they are easily accessible while the rest of our gear is stored in a locker in a single large mesh bag. When it’s time to dive, our side deck becomes a mini dive shop as we assemble our gear.

We leave our weights out of the BCDs to lighten the load as much as possible when transferring to the dinghy (be careful never to lift from the first stage, use the handle on your BCD or the yoke on the tank instead to ensure you don’t damage the tank’s O-ring).

Many of the best dive sites have mooring buoys that you can use to tie up the dinghy. If you find a site that doesn’t have a mooring, use a small grapple-style anchor with several feet of chain and some small diameter line to anchor the dinghy. Just be sure to check that your anchor is well set and not damaging live coral.

On larger boats, it’s common to don your dive gear on the boat and back-roll off the side, but in a cramped and unstable dinghy this can be difficult. Instead, we’ve fixed a length of shock cord to each of our BCDs with a bronze clip. This five-minute project allows us to partially inflate our gear and roll it into the water where it can float securely attached to the dinghy until we’re ready to get in and begin our dive.

The first time we put our BCDs on in the water felt strange and awkward, but we quickly found it to be much easier. At the end of the dive, we reverse the procedure, re-clipping the BCDs to the dinghy and easily climbing in without worrying about our gear floating off.

Diving without a guide can be challenging, and yet it’s an immensely rewarding activity as a cruiser.

To keep it fun and comfortable, we always follow a few simple safety steps before submerging. We always start by checking our equipment on the boat before leaving. After setting up our gear we open our tanks to verify tank pressure and pressurise the system. If an O-ring is going to split, it will usually do so at this point, so better it happens on the boat than at the dive site. We then make sure our regulators and inflator hose are working properly.

Diving with reef sharks. Photo: voyagesofagape.com

As we get ready in the dinghy, we take an extra minute to set up a dive flag and observe if there is a current. Usually, it is better to start the dive swimming against the current, so your return trip is easier.

We also use this time to talk about our dive plan, which direction we will swim, our planned depths, times, and make sure all participants are feeling comfortable. Once in the water, we do a final surface check of our gear – and our buddy’s gear – before descending.

If a diver is going to have trouble, it is usually during the descent. Whether it’s inadequate weight, trouble equalising, or just being nervous, it’s especially important to pay close attention to your dive buddy during this part of the dive.

Joshua Shankle and his wife, Rachel, are cruising the world on their 42ft Tayana Agápe. Photo: voyagesofagape.com

After the descent, we make sure to make eye contact again, giving the okay sign, signalling we are ready to continue our dive. Make sure to regularly check-in and verify that everyone is feeling good and has adequate air throughout the dive. Lastly, plan to arrive back at the dinghy with plenty of air. We follow the rule of thirds: 1/3 outgoing, 1/3 returning, and 1/3 to surface.

This helps to ensure that we have a good reserve should something happen at any point during our dive. When diving as a couple, this is especially important, as you only have each other’s tank if your gear should ever fail.

It’s important to always dive with a buddy and within your limits. Communicate if you are feeling nervous or not comfortable with any part of the dive plan, follow your gut instincts, and don’t push past your comfort level.

Diving Kit list:

BCD (buoyancy compensation device): a backfill BCD with an integrated emergency regulator on the inflater hose will be more compact and eliminate an extra hose. The Oceanic Biolite weighs in at only 2.5kg.

Buy the Oceanic Biolite from Amazon (US)

Buy the Oceanic Biolite from Amazon (UK)

Note: We may earn a commission when you buy through links on our site, at no extra cost to you. This doesn’t affect our editorial independence.

Mask: any mask that fits your face will do, but a single lens mask will open your field of view and can make diving seem less claustrophobic.

Regulator and first stage:

The Cressi AC2 is robust and affordable.

Buy the Cressi AC2 from Amazon (UK)

Buy the Cressi AC2 from Amazon (US)

Dive computer: depth, tank PSI or BAR, time, and a compass are important features. We recommend Garmin Descent dive watches.

Buy Garmin Descent dive watch from Garmin

Fins: also a personal choice, but split fins are preferable.

Dive flag: a very important piece of a dive kit that is often overlooked

Safety sausage: an inflatable float that will signal your exact position even before you surface.

Wetsuit: depending on water temperatures and personal preference, a wetsuit is advisable. A hood, gloves, and booties are also good to have in colder temperatures.


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