IT WASN’T A FACE-OFF, it was a rout. We were finishing a tremendous dive on a lovely wall near the Sudan border, and we’d seen a nice big humphead parrotfish as we were coming up to safety-stop depth.
Big pelagics – mostly large jacks but also tuna and a handful of sharks, were coming in and out of the blue as we came under the liveaboard at 5m.
Then came that distinctive sound – bubble-wrap being crackled, mixed with the creaking of a tree or a hinge, blended with a whistle.
Panic ensued among the jack and the sharks, then half a dozen grey shapes burst out of the blue, barrelling in at top speed – bottlenose dolphins.
They didn’t seem interested in hunting, they just erupted into the middle of the sharks and jack, scattering them.
It was a gang, pushing weaker animals around, for no apparent reason other than to show who’s boss.

HOW DOLPHINS WORK
It’s easy to understand our fascination with dolphins – the beauty of form demonstrating function. It’s the sleek lines, the power, grace, intelligence, curiosity about us, and that fixed “smile”.
A dolphin’s body is the most powerful swimming machine on earth, far more so than any tuna’s or shark’s.
A heavy backbone with huge slabs of muscle attached drives a surprisingly small, stiff, foil-like tail.
The upstroke creates a wave, which the downstroke or recovery stroke then surfs down.
You can’t drive this much muscle if you extract your oxygen via gills – water can’t hold enough oxygen – so you have to breathe air. Dolphins explosively exchange huge lungfuls of the stuff, pulling more of the oxygen than we can from each breath into their rich, dark blood.
As any human freediver can attest, it’s a humbling experience swimming with dolphins. The most adept, trained human is clumsy and graceless.
With smaller dolphins our awkward movements often seem to scare them, and with larger and bolder ones we don’t seem to be capable enough in the water to hold their interest.
The difference in breath-hold ability between humans and most dolphins is not as great as you might imagine.
Their oxygen-extracting ability beats that of any marathon-runner, but is offset somewhat by the demands of their mass of muscle.
Most are poorer divers (and less agile) than true seals, and certainly can’t out-dive the beaked whales or the sperm whales. They are tied to air at the surface by their energetic bodies.
What sets them apart from human freedivers is their slippery shape, with so much less drag than we have, allowing that beautiful, effortless glide through the water.

A WORLD OF SOUND
To understand the dolphin’s success, you have to look at its head.
Being buzzed by a dolphin is one of life’s highs. You feel and hear vibrations running right through you. The skull of a dolphin is effectively a sonar dish, with the rounded “forehead” melon a focusing lens for the emitted sound pulses, and the smile-shaped lower jaw an oil-filled receiver, catching and funnelling the echoes returning from the environment and the prey.
As mere humans, it’s difficult even to conceptualise what a sense like this might feel like.
Our sonars produce pulses of sound at specific frequencies. Low frequencies (deep sounds) can penetrate further through the water, but can give only a rough picture of large objects. High frequencies (mainly beyond our hearing range) give high-resolution “imaging” but can penetrate only a few tens of metres. Our sonar arrays are single-frequency and expensive.
Dolphins, on the other hand, can work continuously through an incredible range of frequencies, allowing long-distance communication, group co-ordination and social calling as well as a clear view of their surroundings and prey.
To this sense, our bodies are semi-transparent – although if you’re coy about a dolphin looking through you, then wearing a spongy wetsuit probably deadens the picture.
Many dolphins apparently prefer girls to boys, and they often pay particular attention to pregnant ladies.
They can read your heartbeat, your muscle tension and may be able to see what you had for breakfast – I like to think of dolphins discussing what Shreddies might be.
It’s an incredible sense, and one that no other marine animal has. Most marine animals sense vibrations, but passively at close range.
Many marine animals detect – smell – chemical signals. Sharks and rays can, at close range at least, detect electromagnetic fields. But it’s vision and visibility that limit how well almost all marine animals can interact with their world, and only the sounds of dolphins and whales move beyond this.

RULERS OF THE SEAS
Add bigger brains and greater co-ordination as hunters than any other marine animals, and you can see how dolphins rule the seas.
For millions of years, sharks, big squid and giant pelagic fishes have been struggling to compete with these air-breathing upstarts for space at the top of the world’s ocean food-webs.
These others have been out-gunned, out-muscled and outsmarted, surviving by sheer efficiency – near, if no longer at, the apex of their eco-systems.
In the past 30 years, we’ve wiped out between two-thirds and 90% of the populations of most sharks and large fishes, while killing fewer dolphins.
We’ve eliminated the competition, and dolphins are doing OK.
Few large land predators have ever had populations in the millions, yet eight species of dolphins do. Our best guess is that there are around 25 million dolphins and porpoises worldwide.
Their energy demands mean that they consume almost as much fish and far more squid than humans do worldwide.
Even with us eating into their food supplies, they compete with humans and seals as Earth’s dominant ocean predators.
Sometimes we attack them, rather than merely competing. Driftnets and longlines drown tens of thousands of dolphins each year. Fleets follow and surround dolphins in order to be led to tuna and other fishes.
The Faeroese are condemned every year for continuing their annual drive of around 1000 pilot whales inshore to be killed for food.
The recent film The Cove highlighted the Japanese dolphin drive at Taiji, not only for food (the movie points out that, as large, long-lived predators, dolphins bio-accumulate toxins and are as such rather an unhealthy food source) but to supply dolphinaria.
Keeping an intelligent animal that communicates, socialises and sees its complex world through sound in a concrete, sound-reflecting box seems akin to the kind of sensory-deprivation torture found in spy novels.
The justification is that few people get to see dolphins in the wild – if we are to care about them, then seeing them up close like this can generate inspiration.
Dolphinarium inmates are in poor condition, and have short lives of depression and often illness, despite the efforts of trainers and vets genuinely dedicated to their well-being. Daily doses of stress-relieving drugs dull the senses, but probably not enough.
There are one or two poorly documented cases of wild orcas attacking people in the wild, but a couple of dozen cases of injury, and at least four deaths, from orcas kept in dolphinaria.
Fortunately, some of our interactions with dolphins are positive for both parties. We like them, and they seem to like us. So how do you go about snorkelling or diving with dolphins

DOLPHIN INTERACTIONS
They may be abundant, but dolphins are constantly on the move, and usually disinclined to stick around to interact with humans. We can’t swim at their pace, so most human-dolphin interactions are from boats.
Experienced operators usually say hang still and let the animals take an interest in you. It is pointless and counter-productive to chase dolphins swimming, and any encounter is entirely at the whim of the animals – something that doesn’t always sit well with us humans.
There are places where swimmers are not permitted to interact with dolphins and whales, to avoid stressing the animals, yet boats full of dolphin-watchers are allowed to buzz around the animals, which is far more of an intrusion and danger than snorkellers can be.
Most of the world’s dolphins are small, long-beaked tropical dolphins – mainly the spinner, striped and spotted varieties. Similar common dolphins spread into somewhat cooler waters.
Unfortunately, most are found over deep water far from shore, and/or tend to be on the move – finding enough food in tropical seas is a full-time job.
Many of these small (human-sized, although somewhat more solid and heavier) dolphins are shy of snorkellers and divers.
Huge populations of common dolphins overwinter around the UK’s shelves – offshore, and at a time when divers and snorkellers tend not to be venturing out.
There are a handful of places where you can interact with these dolphins in relatively benign environments: Galapagos and Cocos Island, as well as South Africa’s sardine run are regular feeding areas, with frequent interactions.
Egypt’s Sha’ab Samadai, off Marsa Nakari, has a resident population of up to 500 spinner dolphins, while White Sand Ridge on the little Bahama Bank has a resident population of spotted dolphins.
The bottlenose dolphin, aka Flipper, is larger and bolder than these smaller relatives, is the most widespread dolphin, and probably the one most likely to interact with people.
I’ve had some success in getting bottlenose dolphins interested by diving down and doing spins or somersaults – something that would probably scare off smaller dolphins.
Tropical bottlenose dolphins are often seen on Red Sea dives, and Shark Bay in western Australia has a resident population. The larger coolwater bottlenose dolphins live in murkier, more productive water, and the UK has a handful of resident groups, totalling perhaps a few hundred individuals, notably off west Wales and the Moray Firth.
Not an obvious choice for interactions, but pilot whales (the term should probably be “pilot dolphins”) are abundant, widespread and, in a couple of places, interact with snorkellers.
The biggest populations are in cool, deep waters of the north Atlantic, where they chase squid at depth – not particularly accessible. However, there are resident populations in the Canaries and Gibraltar.
Steve Warren has been working with the Gibraltar pilots in the past few years, and has found that pairs of snorkellers, dropped ahead of them by experienced skippers, can sometimes attract their attention and lead to superb interactions.
Some, however, have found that pilots can occasionally be intimidating, with bubble-burst and tail-wash threats. A couple of snorkellers in the Mediterranean and Canaries have been dragged down as temporary “playthings” by them – not harmed, but rather shaken!
Short-beaked dusky and white-sided dolphins and their relatives dominate dolphin fauna in cool seas. They are abundant in both hemispheres but, like our wintering common dolphins, tend to be where divers aren’t. Kaikoura in New Zealand is one notable spot where people can interact with dusky dolphins, and off Christchurch you can snorkel with the rare, diminutive Hector’s dolphin.
The largest dolphin, and the world’s top marine predator, the orca, is found all over the world, and visits warm waters, but is mainly a coldwater animal – only cold seas can provide enough to feed these giant dolphins.

ORCAS ARE KNOWN AS “killer whales”, although this is incorrect for three reasons. Firstly, they are dolphins, and other dolphins are called dolphins.
Secondly, all dolphins (and other whales) are “killers” – they are all predators. Thirdly, “killer whale” comes from a mistranslation of “whale-killer”, given by early whalers due to orcas’ habit of attacking large whales.
There are several well-studied orca populations in cold seas around the world, but in most areas people are not permitted to enter the water with them.
Tysfjord in northern Norway was an area in which snorkellers could interact with orcas hunting herring, but in the past few years, shifting migration routes have made this less certain.
Not in the dolphin family, but a close relative, the Arctic beluga is an animal with which you can interact in a couple of (cold) places.
The beluga has the unusual habit of gathering to moult in a handful of shallow estuaries every July and August – the most accessible being near Churchill, in the Canadian Arctic.

DOLPHINS OF THE WORLD
1. Hector’s
2. Commerson’s
3. Haviside’s
4. Chilean
5. Irrawaddy
6. Australian Snubfin
7. Pygmy orca
8. Electra
9. Northern right whale
10. Southern right whale
11. Dusky
12. Peale’s
13. Pacific white-sided
14. Atlantic white-sided
15. Hourglass
16. White-beaked
17. Short-beaked common
18. Long-beaked common
19. Risso’s
20. Long-beaked bottlenose
21. Bottlenose
22. Harbour porpoise
23. Vaquita
24. Burmeister’s porpoise
25. Spectacled porpoise
26. Dall’s porpoise
27. Fraser’s
28. Striped
29. Clymene
30. Spinner
31. Pantropical spotted
32. Atlantic spotted
33. Rough toothed
34. Indo-Pacific humpbacked
35. Atlantic humpbacked
36. Finless porpoise
37. Tucuxi
38. Long-finned pilot whale
39. Orca
40. Orca type B
41. Short-finned pilot whale
42. Orca type C
43. Orca type D
44. Pseudorca