Life is fleeting.

Beneath a precipice, that fronts the wave, / with limpid springs inside, and many a seat / of living marble, lies a sheltered cave, / home of the Sea-Nymphs. In this haven sweet / cable nor biting anchor moors the fleet.

It's apparently a metaphor for something uncatchable, light of body and fleet of foot.

When now the Gods have made proud Ilion fall, / and Asia's power and Priam's race renowned / o'erwhelmed in ruin undeserved, and all / Neptunian Troy lies smouldering on the ground, / in desert lands, to diverse exile bound, / celestial portents bid us forth to fare; / where Ida's heights above Antandros frowned, / a fleet we build, and gather crews, unware / which way the Fates will lead, what home is ours and where.

A fleet of alien communists has arrived looking for someone named Posadas.

Our eyes met just fleetingly.

But when the day closed in, and the night put an end to their banquet, it suddenly seemed to them that all the earth was in a blaze; and from the open came a sound of splashing oars, as if a great fleet were approaching.

The mythical Kraken, thick as a ship and three times as wide, once made an attack on Christopher Columbus's fleet... giving Columbus no choice but to eat him.

Algeria has the capacity to expand its fleet.

Darius organized a fleet of five hundred ships.