Why does Edwin say “we should have stayed in the water longer” to Cole at the end of Chapter 18?

Edwin snays this because if they'd stayed in the water longer, Cole might have "more" intelligent questions.... he may even have been able to answer a few on his own.

Edwin smiled.“That’s the first intelligent question I’ve heard you ask all morning.” He shrugged.“Maybe Garvey and I want redemption for our own mistakes in life. We were never able to help those we hurt.”
“Well, it’s my life,”Cole said.“Not yours.”
“We should have stayed in the water longer,”said Edwin, heading down the hill toward camp.