V berth mattress - We read in sailboat forums about the Spa Sensations memory foam mattress from Wal-Mart. We got the 8&quot; Spa Sensatins Memory Foam Mattress for $260 (now $199). We measured the dimensions of the v-berth, then drew it on the mattress. He cut the mattress with an electric bread knife which was easy and didn&#x27;t tear it.