Or, "a set wave is a terrible thing to waste."
When the surf is pumping well overhead, the crests are feathering and wind is howling up the faces, there's very little chance to look back and see if you're snaking someone by taking off.You know someone was sitting deeper than you, but have no idea whether they're catching it or not. There's no time to look; it's way critical and your attention needs to be in front of you and down the line. Not only that, you may not even be able to see them anyway if they are there, backdooring it behind a curtain of spray or coming out of the sun.
That's why one of the kindest and coolest things you can do is to simply yell "Go!" if you are unable to catch a good one, but there are surfers inside of you who can, or could. Split seconds count, and this gives the insider a precious moment to stroke in.
The flip side, of course, is to say "got it," "yeah!," whistle loud, hoot, or otherwise let those inside of you know that it would be fully lame to go, cause you're on it.
An uninvolved surfer sitting nearby can also help. "He missed it, go!"