Here is a short glossary of water vessels:

Boat: A seagoing vessel under 150' in length.

Dinghy: A small boat usually without a motor-most times rowed by oars but not always.

Lifeboat: Can be a zodiac or tender used to carry passengers if they need to abandon ship.

MV or M/V: Motor or Marine Vessel motored by a diesel/gas motor or mechanical propulsion.

MY or M/Y: Marine Yacht is used for racing or cruising. Run by diesel/gas motor, wind or mechanical propulsion.

Skiff: Any of various small boats; especially : a flat-bottomed rowboat.

Ship: A seagoing vessel greater than 150' in length. Used for luxury cruises, import and export.

Tender: Small boat with motor to transfer passengers from a boat/ship to take them to shore or to a boat.

Zodiac: Inflatable rubber boat with a small motor that moves quickly to divers in water to pick them up.