Sony Japan today introduced a successor to the NWD-W253 Walkman waterproof MP3 player. Known as the Sony NWD-W263 Walkman, the new player is 25-percent smaller than the previous model. Weighing at only 32 grams, the new Sony NWD-W263 Walkman supports MP3, WMA, ATRAC, Linear PCM and AAC files and provides a 4GB of storage space. Its rechargeable battery offers up to 8-hour of continuous playback time. No word on pricing at this time.