Greek proverb: Αἰγιαλῷ λαλεῖς

Here's a saying from Apostolius, C1.84, with a Latin version from Clavis Homerica. The image is from David Sifry at Flickr. Here are some more Apostolius proverbs.

Αἰγιαλῷ λαλεῖς.
Littori loqueris.
You might as well talk to the shore.