| Actor | Character |
|---|---|
| Marzena Godecki | Neri |
| David Hoflin | Jason Bates |
| Jeffrey Walker | Brett Bates |
| Alex Pinder | Winston Seth |
| Kerry Armstrong (season 1 and 2), Liz Burch (season 3 and 4) | Dianne Bates |
Season 1[]
| Actor | Character | Episodes |
|---|---|---|
| Jacalyn Prince | Vanessa Lane | 2–13 |
| Guy Mallaby | Damien Geoffries | 1–13 |
| Andrea McEwan | Lee Lucas | 1–13 |
| Bryony Price | Jodie | 1–13 |
| Joel de Carteret | Jake 'Froggy' Reilly | 1–13 |
| Cassandra Magrath | Zoe Kondelos | 1–13 |
| William McInnes | Commander Jack Lucas | 1–13 |
| Miki Oikawa | First Officer | 1–13 |
| Melvin J. Carroll | Second Officer | 1–13 |
| Nina Landis | H.E.L.E.N. | 1–13 |
| Rodney McLennan | Spotty Kid | 1 |
| Mary Ann Russell | Pilot | 1 |
| Doris Younane | Celia | 2 |
| Steve Broomhall | Search Officer | 2 |
| Peter McDonald | Father | 5 |
| Leilani Krans | Young Neri | 5 |
| Tim Robertson | Blunt | 6 |
| Neil Melville | Lambert | 6 |
| Elliot Hayes | Billy | 6, 10–13 |
| Charles Tingwell | Mr Carmody | 7 |
| Nick Carrafa | Haig | 7 |
| Peter Webb | Max | 7 |
| John McCulloch | Zenco P/A | 7 |
| Tenley Gilmore | Valda | 8 |
| Emanuela Leoni | Valerie | 8 |
| David Watson | Make Crew Member | 8 |
| Leila Koren | Neri Look-A-Like | 8 |
| Jermaine Herbohn | Sam | 9 |
| Lyndon Daly | Kevin | 9 |
| Rhys Hine | Matt | 9 |
| Michael Richards | Nick | 9 |
| Louise Bennetto | Gift Shop Owner | 9 |
| Megan Holloway | Shop Attendant | 9 |
| Bianca Griffin, Todd Pilkington | Couple No. 1 | 9 |
| Lisa Thorpe, Phillip Bartlett | Couple No. 2 | 9 |
| Abbe Holmes, Hamish Hughes | Cinema V/O | 9 |
| Andrew Duffin | Smithfield High | 9 |
| Frederick Duffin, William Duffin, Daniel Glutchen, Dennis Hunter, Gardon Hunter, Timothy Wason, Sam Wason | Corroboree Group | 9 |
| Helen Jones | Jan Slater | 10 |
| Stephen Hall | Medical Officer | 10 |
| Rebecca Strok | ORCA Nurse | 10 |
| Nicholas Bell | Dr. Hellegren | 12–13 |
| Fred Whitlock | Johansson | 12–13 |
| Ashley Firman | Senior UBRI Guard | 12–13 |
Season 2[]
| Actor | Character | Episodes |
|---|---|---|
| Nicholas Bell | Dr. Hellegren | 1–13 |
| Jacalyn Prince | Vanessa Lane | 1–13 |
| Joel de Carteret | Froggy | 1–13 |
| Cassandra Magrath | Zoe | 1–13 |
| Anthony Hayes | Mick Byrne | 1–13 |
| Kristy Barnes Cullen | Joanne | 1–13 |
| Sam Johnson | Rocky | 1–13 |
| Claudia Buttazzoni | Kimberly | 1–13 |
| Terry Serio | Captain Sam Phillips | 1–13 |
| Pamela Rabe | Commander Byrne | 1–13 |
| Caitlin McDougall | Lieutenant Borg | 1–13 |
| Miki Oikawa | First Officer | 1–13 |
| Christopher Kirby | Second Officer | 1–13 |
| Nina Landis | H.E.L.E.N. | 1–13 |
| David Whiteley | UBRI Scientist | 2 |
| Robert Cooper | Neri's Father | 3 |
| William Gluth | Forsyth | 4–13 |
| David Hudson | Johnny Mack | 4 |
| Cordon Hunter | Young Johnny Mack | 4 |
| Vanessa Girling | Baby Mera | 4 |
| Lauren Hewett | Mera | 5–13 |
| Sonya Suares | Liselle | 5–13 |
| Bob Newman | Dr. Gabriel | 5–6 |
| Yew Ling Tan | Li Cheng | 5 |
| Eric Milliken | Joshua | 5 |
| Mitch Deans | Limousine Driver | 5–6 |
| Andrew Bibby | Steve | 6 |
| Daniel Bowden | Patrick | 6 |
| Dennis Lenox | Guard | 6 |
| Linda Ross | Counsellor | 7 |
| Adrian Smith | UBRI Assistant | 9 |
| Anthony Hawkins | Searcher #1 | 11–13 |
| Nicola Paull | Searcher #2 | 11–13 |
Season 3[]
| Actor | Character | Episodes |
|---|---|---|
| Sudi de Winter | Benny Malcovitch | 1-26 |
| Brooke 'Mikey' Anderson | Cassandra Clayborn | 2-26 |
| Tony Briggs | Dave Hartley | 1-26 |
| Olivia Hiddlestone | Sallyanne Taylor | 2-26 |
| Jeremy Angerson | Kal | 3-26 |
| Lauren Hewett | Mera | 21-26 |
| Joelene Crnogorac | Lena Hellegren | 2-26 |
| Nicholas Bell | Dr. Hellegren | 1-26 |
| Nadja Kostich | Kellar | 1-26 |
| Bruce Hughes | Commander Wellington | 1-26 |
| Nina Landis | H.E.L.E.N. | 1-26 |
| Verity McIntyre | Morgan Clayborn | 2-26 |
| Jean-Pierre Mignon | Dr. Malcovitch | 2,4,10,14,24,26 |
| Susan Gorence | Mrs. Clayborn | 2,8,11-13,24,26 |
| John Morris | ORCA Surveyor | 1 |
| Ian Wilmoth | UBRI Man #1, UBRI Guard | 1,9,26 |
| Eddy McShortall | UBRI Diver #2 | 1,5,7-8,11-14,17 |
| Carol Stahl | Tribunal Member | 1,8,17 |
| Desire Vincent | Tribunal Member | 1,8,17 |
| Davin Taylor | ORCA Surveyor's Assistant | 1 |
| Peter West | UBRI Diver #1/Surveyor's Assistant | 1,5,7,11-13,17 |
| Martin Copping | ORCA Cadet, Orky, ORCA Kid | 2-3,5,9-15,17-19,21-22,24-26 |
| Nelao Hishongwa | ORCA Cadet | 2-3,5,10,12,18 |
| Cecille Johnson | ORCA Cadet, Georgie | 2-3,5,10,12,15,18,21-22,24 |
| Darius Mendoza | ORCA Cadet | 2-3,5,10,12,18,21-22,24 |
| Doug Penty | UBRI Guard, UBRI Attendant | 3-4,9,19-20 |
| Natalie Gauci | ORCA Girl | 3 |
| Sally Bayes | Larissa | 4 |
| Karen Corbett | ORCA Facilitator | 4 |
| Joel Williams | Butler | 4 |
| Mitch Deans | UBRI Diver | 5,7-8,11-14,17-18 |
| Carolyn Bock | Kraya | 6 |
| Qliong Truong | Rang | 10 |
| Duy Ngoc | Rang | 10 |
| David Kirkpatrick | Immigration Official | 10 |
| Harriette O'Kellow | ORCA Bridge Officer, Duty Officer | 10,12 |
| Yvonne Virsik | UBRI Guard, Kellar's Assistant | 10,13,19 |
| Jonathon Brooks | Moose | 11 |
| Defah Datner | Mouse | 11 |
| Jason Raftopoulos | Snake | 11 |
| Luke Jackson | Kissing Boy | 11 |
| Alejandra Nicolazzo | Kissing Girl | 11 |
| Renai Caruso | Myreka | 11 |
| Bill Scentrine | ORCA Newsreader | 12 |
| Kerri-Lee Andrews | UBRI Woman | 12 |
| Saskia Post | Hypnotherapist | 13 |
| Roger Boyce | UBRI Scientist | 14 |
| Robin Gibbes | Camilla Sabato | 15 |
| Jon English | Doug | 16 |
| Petra Jared (Yared) | Patti | 16 |
| Colleen Hewitt | Faye | 16 |
| Jeffrey Frazer | UBRI Worker | 16 |
| Miki Oikawa | First Officer | 16 |
| David Watson | Professor Danks | 17 |
| Tenley Gillmore | Dolores | 18 |
| Rick Anderson | UBRI Diver | 18 |
| Zellie Thompson | UBRI Diver | 18 |
| Graham Calbury | UBRI Driver | 20 |
| Prudence Mazorodze | ORCA Cadet | 21-22,24 |
| Shanyn Asmar | Searcher | 21-22,26 |
| Kirk Alexander | Searcher | 21-22,26 |
| Nikita Rotumah | Lilah | 21 |
| Luke Carroll | Bobby | 21 |
| Warren Owens | Ernie | 21 |
| David Bradshaw | Faceless Man | 22 |
| Kee Chan | Mr. Lee | 23-24 |
| Pia Manning | Receptionist | 23 |
| Pasha Elmahdy | Cleaner | 23 |
| Michaela Rupina | ORCA Newsreader | 25-26 |
| Dan Logan | UBRI Assistant | 25 |
| Texas | UBRI Guard Dog | 25 |
| Shane Alexander | Diver | 26 |
Season 4[]
| Actor | Character | Episodes |
|---|---|---|
| Brooke 'Mikey' Anderson | Cassandra Clayborn | 1-26 |
| Damien Bodie | Louis Danton | 1-9,11-18,21-26 |
| Tharini Mudaliar | Shersheba | 1-26 |
| George Henare | Malakat | 1-26 |
| Mark Neal | Agent Jake Shelby | 1-13,17-26 |
| Brenda Monaghan | Agent Elly Hauser | 1-13,18-26 |
| Tony Briggs | Dave Hartley | 1-2,5,7,9,14,19,23,25-26 |
| Nina Landis | H.E.L.E.N. | 1-18,20-26 |
| Paul Sonkkila | Richter | 1,4-13,17-26 |
| Michael Veitch | First Officer Danton | 1-3,5-6,9,12,22,25-26 |
| Gregory Ross | Paul Bates | 2-6,9-13,15-16,21-22,25-26 |
| Marie-Louise Walker | Shalamorn | 2,6-7,9,11-13,20,26 |
| Lauren Hewitt | Mera | 14-26 |
| Heath Bergersen | Jakamarra | 5,9-10,23,26 |
| Rhona Rees | Ilona | 17-26 |
| Barry Friedlander | Garron, Garren | 6,9,15-18,20,22,25-26 |
| Big Bad Ralph | Horace | 3 |
| Michael Joshua | Tour Guide | 3 |
| George Vidalis | Chieftain | 4 |
| Rodney Afif | Bedouin | 4 |
| Ramez Tabit | Bedouin | 4 |
| Josie Palermo | Belly Dancer | 4 |
| Nina Godino | Bedouin Child | 4 |
| Harriette O'Kello | ORCA Officer | 5-6 |
| Zev Eleftheriou | Captain | 7 |
| Belinda Davey | Dr. Laviche | 11-12 |
| Jackie Kelleher | Female Elder | 14,16 |
| Anthony Hawkins | Male Elder | 14,16 |
| Molly McCaffrey | Emma | 15 |
| Tom Hutchings | Luke | 15 |
| Victor Bizzotto | Computer Technician | 15 |
| Philip Reilley | Camper | 18 |
| Catherine Wilkin | Madame President | 19,21-22 |
| Ric Anderson | Commando | 19 |
| John Harvie Morris | Alien, Commando, Invasion Captain | 22-23 |
| Philip Stammers | PRAXIS Technician | 23 |
| Brett Williams | Countdown Officer | 23 |