Select the most appropriate one-word substitution for the given group of words. 

A small fleet of ships or boats.

Flotilla

The correct answer is flotilla.

• Grove is a small wood or group of trees.
• Fleet can refer to a large number of ships or vehicles, or to a group of ships or vehicles that are part of a navy.
• Torrent is a strong, fast-flowing stream of water.

The word flotilla is derived from the Spanish word flota, meaning "fleet". It is a small group of ships or boats, typically used for a specific purpose, such as a military operation or a scientific expedition.