why doesn't my washing machine spin when it's full of water?
Are you sure it's not doing exactly what it's supposed to do? It's not supposed to spin during the wash part of the cycle. When it's full of water it's supposed to agitate.  I don't have a Whirlpool washer, so I don't know exactly how yours agitates, but usually this means it turns back and forth, a little one way, a little the other. Once the wash part of the cycle is done it should drain, then spin. Then it will refill and go through the same routine to rinse.