From above, the first thing you notice is the blue. The mineral-rich water reflects a clarity unusual for tropical lakes, a deep cerulean that shifts to turquoise in the shallows. But look closer at the northern shores and the palette changes entirely. Microbial mats -- thick communities of bacteria -- carpet the lake margins in bands of orange and red. The colors come from a tug-of-war between chlorophyll and carotenoid pigments, their ratios shifting with water temperature so that the shoreline looks different from one season to the next. The pH runs above 8.0, alkaline enough to favor these particular organisms over competitors. It is an ecosystem painting itself in real time, rewriting its edges with every temperature fluctuation.

What maps call Lake Ayamaru is actually three lakes -- Jow, Semitu, and Yate -- threaded together across the central basin. Jow stretches roughly seven kilometers long and two wide, the largest of the group, its surface occasionally fogged by temperatures hovering around 71 degrees Fahrenheit. A tree-covered island called Kaymundan sits near its center, a green dot on blue. The village of Greemakolo clings to the northwestern shore, and from here the Ayamaru River begins its journey toward the lowlands. Then there is Lake Hain, a pair of lakes fed by the Framu River, where the water tells a different story altogether. Temperatures reach 100 degrees Fahrenheit. Mist rolls across the surface in thick curtains. These are hot springs, geothermally heated, and standing at their edge you feel the warmth rising before you see the water.

Beneath the surface, small fish carry colors as vivid as the microbial mats above. Boeseman's rainbowfish is the most famous -- half blue-grey, half blazing orange, as if two different species were fused at the midline. Dutch ichthyologist Marinus Boeseman collected the first specimens, and the species now bears his name. It exists only here. During the 1980s and early 1990s, the aquarium trade discovered these fish, and local collectors harvested over a million annually. By 1989, an estimated 60,000 males were captured each month for shipment to exporters in Jakarta. The species landed on the IUCN Red List as Endangered. The Indonesian government eventually restricted collection, and captive breeding programs now supply most of the aquarium market. Three other endemic fish share these waters -- the Ajamaru Lakes rainbowfish, the Vogelkop blue-eye, and Hoese's goby -- along with an endemic crayfish, Cherax boesemani, found in no other lake system on the planet.

The people who live around these lakes call themselves Ra ro Maru -- the lake people. They are a sub-tribe of the Maybrat, and their language, also called Ayamaru, is a dialect shaped by the geography it describes. Villages dot the shoreline, and daily life moves with the water: fishing in the shallows of Lake Jow, bathing where the current runs clean, reading the mist on Lake Hain the way a sailor reads clouds. The lakes are not wilderness to the Ra ro Maru. They are neighborhood, livelihood, and calendar. The relationship between people and water here is old enough that the distinction between the two has blurred -- the people named themselves after the lakes, and the lakes carry a name the people gave them. Water upon water. Lake beside lake.