Cremation urns for water burials are biodegradable ash containers that come in all kinds of shapes, sizes and styles. Water burial urns are filled with the cremation ashes and then floated in water where it will sink and disintegrate causing the ashes to spread. Biodegradable urns for water burials can take a few hours or up to a few days to disintegrate and are made of a range of materials. There are water friendly, biodegradable urns made of paper, salt, sand and gelatin. Biodegradable water burial urns are a popular way for families to participate in a deeply moving memorial for a loved one.