The Mar de las Calmas, and why the water is like that
The Mar de las Calmas is the south-western coastal strip of El Hierro, and its name says it: sheltered water. Combined with what lies beneath, it produces some of the best diving conditions in the Atlantic, and not by chance: three geographical factors add up.
The three factors
1. It is in the lee. The trade wind blows from the north-east and this coast faces south-west, protected by the island itself. With no wind striking it, the sea stays flat — hence the name.
2. The bottom drops vertically. El Hierro is the youngest island and the one with least continental shelf: the underwater wall falls away at once. There is depth within a few metres of the shore, which means wall diving with no need for a long boat crossing.
3. Few people, and protection. It is a small island with little tourist pressure and with marine protection designations. Less fishing pressure means more fish and bigger fish, which is exactly what a diver comes to see.
What that produces
Clear water — no suspended sediment because there is no swell to lift it — mild temperatures year round and wildlife close to shore. It is why the island’s reputation among divers far exceeds its size.
What to know if you are diving
- This is wall diving with depth close by. That demands buoyancy control and respect for your dive plan: the wall invites you down and the bottom is not where you expect.
- Certification and insurance. The centres ask for them, rightly: going too deep here is easy.
- The island is small and there are few centres. In season, book before travelling rather than on arrival.
- And a logistics warning: you cannot fly after diving, and El Hierro is reached by plane or boat. Leave margin between your last dive and your departure flight.
If you do not dive
Snorkelling works just as well for the same reason: there is depth and life within a few metres. It is the cheap way to see why this coast has the reputation it has.
Frequently asked questions
›Why is it called Mar de las Calmas?
Because it is in the lee. The trade wind blows from the north-east and that coast faces south-west, sheltered by the island itself, so the sea stays flat. With no swell to lift sediment, the water also stays clear.
›Do you need a boat to dive in El Hierro?
Not always. El Hierro is the youngest island and has barely any shelf: the underwater wall drops vertically within metres of the shore. That allows wall diving without long crossings, and makes snorkelling work well too.
›Can I dive the day before flying?
It is not advisable: you cannot fly after diving, and El Hierro is reached by plane or boat. Leave margin between your last dive and your departure flight, and plan it before buying tickets.