I would say "Okay,Joe." They were the first words heard from the crew following the re-entry communications blackout, which lasted just over seven minutes.(Link for official NASA transcript below.)
"[The first word mission control had that the astronauts were safely back into the earth's atmosphere came through the Patrick AFB aircraft, ARIA No. 4, commanded by Lt. Col. Lawrence L. Brown and assisted by Maj. Harry D. Platt and Maj. Forney D. Yeargier. It should be noted however, that ARIA acquision did not necessarily mean the crew was alive, but was an indication that the CM (Odyssey) had survived the reentry heat.]
JSC PAO: "Coming up now on three minutes until time of drogue deployment. Standing-by for any reports of acquisition. (pause) We got a report that ARIA 4 aircraft has acquisition of signal."
[At about 25,000 feet during entry, the forward heat shield is jettisoned to expose the earth landing equipment (all the parachutes, recovery antennas, beacon light, sea recovery sling) and permit deployment of the parachutes.]
(loop)
Flight: "Capcom, just advise them, standing by."
CapCom: "Odyssey, Houston. Standing by. Over."
Swigert: "Okay, Joe."
CapCom: "Okay. We read you, Jack."
JSC PAO: "That was Jim Lovell responding with the 'Okay, Joe.' (pause) Correction there, that was command module pilot Jack Swigert."
CapCom: "We're looking at the weather on TV, it looks just as advertised. Real good.""
myweb.accessus.net/~090/as13.html#splash no longer exists
http://www.jsc.nasa.gov/history/mission_trans/AS13_TEC.PDF