What did Diego mean when he said 'I have got our secret handshake figured out' to Bree from the second short life of Bree Tanner?

In The Short Second Life of Bree Tanner, there is an underwater cove that Bree goes to with Diego so they don't "burn in the sun" as Riley told them. That was a lie but they didn't know. So Diego and Bree made it into a special BFF club thing. And they needed a secret handshake for their club. So that's what Diego meant when he said, "I have got our secret handshake figured out." Hope this helped. :)