Dangerous 3m storm surf at Merewether Beach amid torrential rain forced the decision to hold a top-level event in a harbour for the first time.
The waves were still dangerous at 2m, but the remaining five heats were nevertheless completed - with the judges cramped into a van away from the elements.
Brazilian De Souza was beaten by Australian pair Jay Thompson and Nick Squires in the final heat of the day after number one seed and reigning ASP World Champion Joel Parkinson just made it through behind Frenchman Marc Lacomare in a tight heat.
"I like the waves here," said Lacomare. "It's good for tube-rides and then there’s big sections of the wave which allow powerful turns and that suits my style.
"To defeat Joel Parkinson in a heat is a very big boost in confidence for me – he’s the champion and hopefully I can beat him again tomorrow on finals day."
Parkinson said: "This is some of the worst weather I've experienced at a surf event but great waves brought the spectators here and I'm stoked to be in the event on the final day.
"Two seconds in the last couple of heats is OK – I've advanced and that’s what counts at this stage."
Organisers hope to move Monday's final, to be contested by the final 12 surfers, back to the beach.
Round of 24 results
Heat 2: Marc Lacomare (France)17.73, Joel Parkinson (AUS)15.5, Maxime Huscenot (FRA)12.67, Felipe Toledo (BRA)10
Heat 3: Dion Atkinson (AUS)17.47, Keanu Asing (HAW)14.90, Matt Wilkinson (AUS) 14.50, Garrett Parkes (AUS) 11.17
Heat 4: Willian Cardoso (BRA)14.46, Julian Wilson (AUS) 12.90, Vincent Duvignac (FRA) 11.13, Ian Gouveia (BRA) 9.6
Heat 5: Pat Gudauskas (USA) 17.67, Alejo Muniz (Bra)15.33, Messias Felix (BRA)14.37, Alex Ribeiro (BRA) 9.2
Heat 6: Jay Thompson (Aus)16.50, Nick Squires (AUS)14, Granger Larson (HAW)10.40, Adriano De Souza (BRA) 6.43