# When we had sailed slowly ... finally arrived with difficulty

You can make explicit that the reason they were sailing slowly and with difficulty was because the wind was blowing against them. 

# near Cnidus

This is an ancient settlement located in modern-day Turkey.

# the wind no longer allowed us to go that way

"we could no longer go that way because of the strong wind"

# we sailed along the sheltered side of Crete

"we sailed along the side of Crete where there was less wind"

# opposite Salmone

This is a coastal city in Crete.