They look like rocks. They aren't. Don't step on them.
They look like rocks. Pale, rounded, often just below the surface near the south shore.
They're alive. Stromatolites are layered colonies of microorganisms — cyanobacteria, mostly — that build up slowly over thousands of years by trapping sediment. Bacalar has one of the last healthy populations in the world.
Most of the damage they've taken is from feet. A person steps on one, the top cracks, the colony stops growing in that spot.
Don't walk on the pale, rounded shapes in the shallows. Don't anchor a kayak on them. Don't use chemical sunscreen when you're swimming near them — the oils kill them slowly.
You can see them clearly at midday, from a kayak, without touching the water.
