The term MATTRESS ALTERNATIVE can be answered with two 8 and 9 letter words: WATERBED and BANKVAULT. A waterbed is a type of MATTRESS that is filled with water, and is often used for medical purposes due to its ability to reduce pressure points. Bankvault is an ALTERNATIVE to a traditional MATTRESS, as it is designed to provide superior support and comfort. It is made from a combination of foam and springs, and is often used in luxury hotels.