| X | Y | Z |
| X-I (USA) | Y8017 (Netherlands) | Zaca (France) |
| XE-8 (GB) | Y8122 (Netherlands) | Zapad (Russia) |
| (XXVIII Ottubre) (Italy) | (Y8262) (Netherlands) | Zapala (USA) |
| Xylonite (GB) | Yambulla (Australia) | (Zarist) (Russia) |
| Yankee (USA) | (Zeearend) (Netherlands) | |
| Numbers | Yankee Fork Gold Dredge (USA) | Zeemeeuw (Netherlands) |
| 1 Mai (Germany) | (Yapura) (Peru) | (Zeldenrum) (Germany) |
| 5 Fukuryu Maru (Japan) | (Yardim) (Turkey) | Zhelesniakov (Ukraine) |
| 198 (GB) | Yarmouth (GB) | Zhongshan (China) |
| (236) (GB) | Yavari (Peru) | Zodiac (USA) |
| 296 (GB) | Yelcho (Chile) | Zuiderzee (Netherlands) |
| 376 (GB) | Yelta (Australia) | (Zuni) (USA) |
| 925 (Germany) | Yeng He (China) | |
| 1262 (GB) | Yhtio (Finland) | |
| 3139 (China) | York Boat (Canada) | |
| Yorktown (USA) | ||
| (YR-28) (USA) | ||
| Yvon Dupre, Jr. (Canada) | ||
| Ysolt (GB) | ||
| (YTL 622) (New Zealand) |
