The right kind of sign

In John 6 we read of the feeding of the 5000 and the aftermath: Jesus withdraws to avoid being proclaimed king, walks on the sea that night to overtake His disciple's boat, and is followed by the crowd that had been fed. Jesus accuses them of just following Him for the sake of food, and this follows:

Do not work for the food which perishes, but for the food which endures to eternal life, which the Son of Man will give to you, for on Him the Father, God, has set His seal.” 28 Therefore they said to Him, “What shall we do, so that we may work the works of God?” 29 Jesus answered and said to them, “This is the work of God, that you believe in Him whom He has sent.” 30 So they said to Him, “What then do You do for a sign, so that we may see, and believe You? What work do You perform? 31 Our fathers ate the manna in the wilderness; as it is written, ‘He gave them bread out of heaven to eat.’”

"What then do You do for a sign?" In light of what happened just the day before, that's an odd question. "Our fathers ate the manna in the wilderness" Hint hint hint.

"You just gave us ordinary bread and fish. We want a jazzier miracle."