O! how I faint when I of you do write,
Knowing a better spirit doth use your name,
And in the praise thereof spends all his might,
To make me tongue-tied speaking of your fame.
But since your worth, wide as the ocean is,
The humble as the proudest sail doth bear,
My saucy bark, inferior far to his,
On your broad main doth wilfully appear.
Your shallowest help will hold me up afloat,
Whilst he upon your soundless deep doth ride;
“Saucy” has undergone a significant shift in meaning between Shakespeare’s time and our own. Whereas to us it means something like “ostentatiously erotic”, the  OED  gives the definition of “insolent towards superiors”.  This latter meaning was current when Shakespeare was writing. 
 Therefore, the speaker’s boat is not worthy for him to sail in. In the extended nautical  metaphor , sailing means composition. 

Sonnet 80