Runners in a half-marathon in London on March 1 might be a little confused at the water stations, where instead of getting water in a plastic cup or bottle, they’ll be handed an edible water-filled pod. The package, which is also compostable, is made from seaweed and plant extracts . You simply bite the corner off and drink.

“What we want to do is have a bulletproof solution—regardless of where it ends up, our packaging will not create negative consequences,” says Pierre-Yves Paslier, cofounder of Notpla, the startup that makes the packaging. “If nature can deal with it if it ends up in the wrong place, that’s the ultimate kind of protection.”

Paslier, a former packaging engineer at L’Oréal, began working on the concept along with designer Rodrigo Garcia Gonzalez in 2013 while they were studying innovation design engineering at Imperial College London and the Royal College of Art. Seven years later, it’s no longer a student project but a viable business. After raising more than $1 million in a crowdfunding campaign last year, the company has just raised its first VC-backed “seed plus” round of more than $5 million.

The designers used a technique from molecular gastronomy to create the package—if you dip a sphere of ice in a mixture of calcium chloride and brown algae extract, an edible membrane forms around the ice, holding everything in place as the ice melts back to room temperature. A small version of the package is designed to break open inside your mouth. “It’s a bit like a cherry tomato,” says Paslier. “You put it in your cheek and bite on it. It explodes, so it’s quite a surprising experience.” The startup partnered with the Scottish whisky brand Glenlivet last year to make a “glassless cocktail” capsule that customers can imbibe along with whisky. The seaweed coating, which is tasteless, can either be eaten or composted.

Larger sachets, used for water in races or at other large events, can be bitten at the corner to drink. “It’s a bit like a lot of soft gels that are you also use in races,” says Paslier. “Squish it in your mouth, and then you can just discard the leftover packaging.” When the London Marathon started using the product last year at some water stations, around 30-40% of runners ate the packaging; the rest threw it away.

If it ends up on the ground, it can either be cleaned up “like leaves,” he says, or it will also quickly biodegrade. That’s very different from most compostable plastic, which needs to be in an industrial composting facility to break down. The company’s name, Notpla, stands for “not plastic” but is also a dig at PLA, a corn-based plastic that acts like regular plastic if it ends up in the ocean; algae also uses far fewer resources to produce than corn or some other materials used in plant-based plastic.

The design isn’t likely to replace the plastic bottles that are ubiquitous in retail stores, for simple reasons of convenience: it holds a small amount of water, and like a piece of fruit, it’s perishable. If it was sitting on a store shelf, it would also have to be washed off to make it hygienic to eat.