This question is about collective nouns used for groups of specific things.
- A school of ships: "School" is a collective noun for fish, whales, dolphins, porpoises (e.
g.
, a school of fish).
Not used for ships.
- A fleet of ships: "Fleet" is the correct collective noun for a group of ships (especially warships, but also commercial vessels) operating together or under one command.
- A bundle of ships: "Bundle" is used for things tied or grouped together, like a bundle of sticks, a bundle of nerves, a bundle of laundry.
Not used for ships.
- A pack of ships: "Pack" is used for animals like wolves, dogs, hounds (a pack of wolves), or for items grouped together for carrying (a pack of cards, a backpack).
Not used for ships.
Therefore, the correct phrase is "A fleet of ships".