Friends of missing Luton man Edward Gillespie say they are trying to stay positive as the search for him continues.
Mr Gillespie, 38, has not been seen since his office Christmas party in Roydon, near Harlow, last weekend.
Relatives reported him missing when he failed to return to his home in Rosslyn Crescent, Luton.
Mr Gillespie was last seen in the early hours of Saturday at the Roydon Marina Hotel at the party, organised by his employers Bureau Veritas.
The search started on Sunday evening after his car was found to still be at the hotel.
The Essex Police marine unit, other specialist search teams and the police helicopter have been searching the River Stort, the river banks, the hotel and hotel grounds.
A police spokesman said high water levels due to recent rain were hampering the river search.
A group of Mr Gillespie’s friends and his brother, Rob, have also been searching the area, and his girlfriend is understood to have flown to the UK from South Africa.
Matt McGrath, 37, of Icknield Way, Luton, a friend of Mr Gillespie since their Icknield High School days, said: “Ed isn’t the type of person to go wandering off on his own.
“We have been looking in rivers and streams in case he might have slipped. We don’t know if he might have been attacked or if there was an opportunist who might have targeted him somehow.
“He might have got a taxi with someone to go to a nightclub, we just don’t know.
“We feel a bit more positive when we are out there looking for him. We’re just trying to get the word out and keep the media spotlight on him. We’re really glad so many people are helping.”
Another friend, Ian Holohan, of Saywell Road, praised the efforts of Essex Police and described the search conditions, saying: “The rivers are very swollen from all the rain, fields are flooded and on some paths we had to turn back because the water meant you just couldn’t go any further.
“As far as I’m aware Ed was in good spirits, there was nothing to indicate he was depressed or might have done anything to harm himself.
“He’s a very upbeat person.”
A Facebook page to raise awareness of the search has been set up at www.facebook.com/HelpFindEddieGillespie