I did a search on Preseed just now and found a site that has a study that says that with Astroglide and Replens after 60 minutes there were no sperm either living or swimming and with KY there were some still alive but none swimming. Now, mind you this site was trying to sell Preseed, but I'd rather be safe than sorry.
ETA: "either living or swimming" that sounds weird. Of course if they're swimming they're alive!

Sorry - I'm in a strange mood today.