The Blue Lagoon is Malta's postcard, and one of the rare places where the photo doesn't lie about the colour: between Comino and the islet of Cominotto, the water is an almost unreal pale turquoise, because the bottom is light sand only a few metres down. What the photo never shows is the crowd. In July and August the cove takes in thousands of visitors a day along two hundred metres of rock. This guide covers both.
What it actually is
Comino is a 3.5 km² island between Malta and Gozo, essentially uninhabited: two or three permanent residents depending on the year, one hotel, no cars, no shops beyond the seasonal kiosks. The Blue Lagoon is the shallow channel separating it from Cominotto, the rocky islet facing it.
There is no sand beach. You get into the water from limestone slabs, via ladders or by walking on the rock. Bring water shoes: the stone is sharp and scorching in full sun.
Shade is virtually non-existent. The kiosk parasols are paid for and go early.

The crowds, unfiltered
This is what the Blue Lagoon looks like on a July afternoon. It isn't a criticism of the place — the water is still extraordinary — but it's information guidebooks systematically leave out.
The peak runs from 11am to 4pm, when the day-trip boats unload their passengers in successive waves. After 4:30pm the cove empties very quickly.

The right slot
Early morning, before the big boats arrive, or late afternoon, as they leave. The light is better too: at midday the sun flattens the colours, while low light brings the turquoise fully out.
Off season, from May to early June or in September and October, the water is still warm and numbers drop to something reasonable.
If you can only come mid-summer and mid-day, walk past the main cove: the coves on Comino's south side, fifteen to twenty minutes on foot, are almost empty and the water is just as clear.
Getting there
Three options, cheapest to most comfortable:
From Ċirkewwa, at Malta's northern tip: the shortest crossing, around fifteen minutes by shuttle boat. The Tallinja bus serves Ċirkewwa from the Valletta terminus, so the whole trip works without a car.
From Marfa, right next door, with the same shuttle operators.
From Sliema or Buġibba, as a day excursion: pricier and longer, but the boat loops around Comino and Gozo, which is worth it in itself. It's also what brings the largest groups into the cove at once.
In all cases these services are seasonal: they run mainly from June to September and thin out considerably in winter.

What to bring, and what isn't there
Water, plenty of it. The kiosks sell drinks but at tourist prices, and they can be mobbed.
Sunscreen and a hat: with no shade, on white rock that throws the light back at you, sunstroke comes fast.
Water shoes and, if you have them, a mask: the bottom is visible several metres down and the fish are there.
There is no cash machine, mobile coverage is decent but not perfect, and toilets are limited. Topless sunbathing is banned in Malta, here included.