Four billion metric tons of uranium sit dissolved in the world’s oceans right now, roughly 1,000 times the total identified in hard-rock mines worldwide. A US startup called Fluxnium just emerged from stealth with a plan to get at it, backed by $7 million in seed funding and chemistry licensed from the US Department of Energy.

The catch: extracting that uranium currently costs more than twice the market rate, and no one has proven it works at commercial scale.

The timing matters. Yellowcake prices have risen approximately 75% over the past five years, according to US Energy Information Administration data. US policy discussions target tripling nuclear capacity by 2050, yet the country imports the overwhelming majority of its uranium from a short list of geopolitically exposed nations.