Sam Shoemaker spent more than a decade growing mushrooms into art before he decided to paddle one across the ocean. Guinness World Records has now certified his 12-foot kayak — grown entirely from the mycelium of Ganoderma polychromum fungus — for the "longest solo journey by a fungal mycelium boat," after the Los Angeles-based artist paddled it 26.37 miles from Catalina Island to Cabrillo Beach on the California mainland in just over 12 hours.
The craft weighed 107 pounds and took seven weeks to grow, following roughly three months of design and testing with Shoemaker's cousin, Laza. The pair used a fiberglass mold and biodegradable textiles to guide the mycelium's growth into a boat-shaped hull, then sealed the finished surface with layers of shellac and beeswax — durable enough to survive a half-day in salt water, but still fully biodegradable once its working life ends.
A test case for living materials
The voyage, completed in August 2025 and only now certified and publicized by Guinness, is less a stunt than a proof of concept. Shoemaker's broader research focuses on mycelium — the thread-like root structure of fungi — as a renewable substitute for plastics, foam and other petroleum-based materials in construction and design. A boat that can carry a person's weight across open water for half a day, builders of biomaterials argue, is a far more convincing demonstration than a lab sample.
It wasn't his first attempt: Shoemaker built an earlier, 15-foot mushroom kayak in 2024 before refining the design for the record attempt. Mycelium-based materials have drawn growing interest from architecture and packaging firms in recent years as an alternative to styrofoam and plastic foam, precisely because they grow into custom molds and then decompose harmlessly, unlike the materials they're meant to replace.
Guinness has not said whether Shoemaker plans a longer attempt. For now, the record stands as a small but literal demonstration that materials grown rather than manufactured can, under the right conditions, keep a person afloat.
