Dive safety

With beautifully clear turquoise waters giving up to 10m clear visibility over rocky and sandy beds there’s some amazing diving from the wilderness islands of Staffa, Treshnish, Ulva and Tiree.

However, there are always safety aspects to consider when diving at sea.

Boat traffic

Whether sedately admiring the seascape or avidly focused chasing down lobster, it can be easy to forget man-made dangers lurking above like boats and propellers.

A marker buoy or dive buoy should be used on the surface to announce a diver’s presence. The buoy is left static, its end weighted to the seabed, whilst the diver swims around the area announced to boat traffic above. Boats are heard well before they are seen as noise travels well underwater and, if a boat is heard, diving should be suspended until a view can be taken on its direction, speed and purpose. Pleasure craft such as water skiers and jet skiers can often be the greatest risk.


Discarded fishing lines and netting is high on the watch list for any diver, however, close to shore, such an object is rare. Tangles during a breathhold are an obvious danger but a dive knife should see to any need. Removing debris reduces the risk for other divers and animals and, if diving the same area frequently, the gesture improves the next dive for yourself as well as others. Anything that can prevent a diver from surfacing should be treated with respect including overhangs, caves, wrecks and piers.

Getting carried away

The power of the sea shouldn’t be underestimated and tides, currents, swell and surge are a safety concern as they can sweep the fittest of divers out to sea or onto rocks. Know the area, the currents and the tides.

– A low tide is useful whilst foraging as it brings food closer to the surface
– A high tide can be fun as it increases the dive area
– Periods between tides can create currents as fast as a river, especially if channeled between rocks or structures
Swell is created far out to sea and results in the grouping of waves in tidy lines that break in shallow areas often making shallow reef dives impossible
Surge is the under the surface up and down movement of water caused by swell and can be dangerous on a reef


Seals are inquisitive animals and sometimes extremely friendly but should not be fed. Seals have large teeth, have been known to nip and recent evidence shows grey seals regularly attack and kill porpoises in large numbers. The injuries of porpoises washed up onshore have been DNA matched to grey seals that seem to strip the bodies for their nutritious blubber. The trick is probably not be mistaken for a porpoise.

Whilst seals have not been known to attack humans there is no evidence to suggest that they will not. Some are 9 feet long and the males are strong animals I would not like to tussle with whilst on a breathhold.


Jellyfish can sting and some are deadly but luckily none of these live in our shores. However, UK waters are warming and, as a result, new species are appearing all the time. Jellyfish common to UK waters are moon jellyfish (Aurelia aurita), Lion’s mane jellyfish (Cyanea capillata), Barrel jellyfish (Rhizostoma octopus), compass jellyfish (Chrysaora hysoccella, blue jellyfish (Cyanea lamarckii), mauve stinger (Pelagia noctiluca) and the by-the-wind-sailor (Velella velella).

If stung get out of the water, lie still to limit the spread of toxins, remaining tentacles should be removed with tweezers (or a clean stick) and apply an ice pack to relieve pain. Most jellyfish stings are mild but if there are signs of chest pain, breathing difficulty or if a sensitive area such as the face or genitals has been stung dial 999 or visit hospital.

Vinegar is no longer recommended as it can trigger unfired stinging cells. Ignore advice to urinate on the sting as this may make it worse. Applying shaving cream to the affected area can help prevent the spread of toxins and swiping the affected area with a credit card to remove nematocysts (small poisonous sacs) that are stuck to the skin (wipe the card clean between each swipe). Pain can be treated with paracetamol or ibuprofen. Jellyfish stings can easily be avoided by wearing a wetsuit.


Weaver fish

Found in shallow sandy or gravel-bottomed waters, the weaver fish has a spiny dorsal fins that punctures wetsuits to deliver a nasty bee like sting.

The pain intensifies as the poison takes effect until it can be an unbearable burning sensation. In this situation it is best to get the sting under hot water, over 40ºC, for 30-90 minutes. The heat breaks down the proteins in the venom and the pain will subside. Paracetamol can be taken. Large spines should be removed from the weaver fish sting using tweezers and then the wound should be washed. The sting should be left uncovered.

Large spines embedded near joints will require a visit to hospital for X-ray. There is a danger of allergic reactions (anaphylaxis) and this too would require A&E. Anti-tetanus prophylaxis injections should be considered if the victim is not vaccinated. Hydrocortisone cream can be applied afterwards for the itching.

Sea Urchins

Sea Urchin puncture wounds can be treated in much the same way as weaver fish stings. The affected area should be soaked in hot water for as hot as can be tolerated – 40ºC is best. Large spines should be removed using tweezers to avoid infection. The small venomous organs (pedicellariae) can be removed by applying shaving foam to the sting and using a clean credit card to swipe the area. Wash the area with soapy water and then leave the wound open to the air.


Eating too much before freediving is not a good idea. Blood is diverted from the brain to the stomach to aid with digestion and this is blood vital to other functions such as absorbing oxygen and powering muscles. Caffeine and energy drinks should also be avoided as they over stimulate the heart making relaxation difficult.


Diving in Hebridean waters is greatly affected by visibility and this can vary from a metre to about 10. When diving in low visibility it is essential to dive on a line and it is recommended that divers attach to it with a lanyard. I never dive in low visibility unless I know the area well. Always dive with a buddy.


Diving plays some curious tricks on the body. Due to the colder temperature of water, blood is withdrawn from our body’s extremities to the core and this triggers the kidneys to react as if the body is overhydrated and, as a result of this, we pee. Additionally to this we sweat and lose water through breath vapour so it is important to drink regularly. Dehydration increases heart rate, makes equalisation harder and can cause headaches.


UK waters can be a challenge as they are, by comparison to other dive areas, colder than many divers are used to.

Maintenance of core body temperature is always an important safety concern as getting cold can affect breath hold efficiency, as blood is diverted to the body’s core and muscles shiver to stay warm. Using a good wetsuit is a diver’s best tool. Maintenance of the suit is important too as crawling across the bed collecting scallops or squeezing through gaps chasing lobster can tear the best of suits. Black Witch repair glue is a fantastic tool for plugging any holes allowing cold water in.


Wind whips up the water surface, creates chop and, when freediving from a rocking boat or a choppy surface, can greatly affect breathing preparation. Wind can also greatly reduce body heat when out of the water. Drink lots and wrap up warm between descents.


There are no large rivers around Ulva, Staffa, the Treshnish Islands and Tiree and the land is rocky so any risk of bad visibility created by mud washed into the sea by rainfall is greatly reduced. Nevertheless, expect cloudier water.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s