Families shopping for an urn before a ceremony at sea run into two words that sound interchangeable and are not quite: water-soluble and biodegradable. Here is the plain answer, and then the detail behind it.
The short answer: if the urn will be placed whole into the sea, it needs to break down readily in water. A biodegradable urn designed for water burial is exactly right — "water-soluble" is simply the kind of biodegradable urn engineered to dissolve within minutes to hours of reaching the water. If you plan to scatter the ashes instead and keep the urn, any urn you love is fine.
Every water-soluble urn is biodegradable, but not every biodegradable urn is water-soluble. Water-soluble urns are made from materials like compressed salt, sand and gelatin, unfired clay, or specially treated paper — they are engineered to absorb seawater, soften, and dissolve completely, usually within minutes to a few hours. Many are designed to float briefly on the surface before slipping under, a moment families often find to be the most moving part of the ceremony.
Biodegradable is the broader word. Bamboo, wicker, banana leaf, and untreated wood urns are all biodegradable, but some of them break down over months rather than hours, and a few are buoyant enough that they do not sink on their own. That does not make them wrong — most urns sold as "biodegradable" for memorial use are made specifically for water ceremonies and behave beautifully. It just means one question matters more than the label.
If the answer to both is yes, the difference between "water-soluble" and "biodegradable" stops mattering. You have the right urn.
Federal rules for burial at sea (the EPA's general permit under the Marine Protection, Research, and Sanctuaries Act) ask two things of families scattering ashes: the ceremony takes place at least three nautical miles from shore, and anything placed in the water — urns, flowers, wreaths — must readily decompose in the marine environment. Nothing plastic, nothing metal, no ribbon or wire. A water-burial urn satisfies this; so does scattering directly from the container and bringing it home.
The paperwork that surrounds this — the permit, the GPS coordinates recorded at the moment of committal, the filing afterward — is handled for you. Families do not need to become experts; you only need the right urn in hand when you step aboard.
Scatter, and keep the urn. The ashes are released from the container at the rail, downwind, with the vessel positioned so the moment is unhurried and private. The urn returns home with you as a keepsake. Any urn works for this — including the one your loved one already rests in.
Commit the urn whole. The urn is placed gently into the water. A water-burial urn will rest on the surface for a short while, then descend on its own. Many families choose this because it gives the ceremony a single, visible moment of farewell — and because it means no one has to open the urn at sea.
There is no wrong choice between the two. Some families decide on the day itself, and that is fine.
Whichever urn you choose, the crew has seen every kind and will handle it with care. You will not be rushed.