The Shell Cove teenager took on Queensland's Jahly Stokes in the under-14s girls decider on Thursday at Woonona Beach.

Jahly proved triumphant in a see-sawing battle, winning 12.07 to 10.27.

Oceanna said surf conditions were ideal, "probably two to four foot maybe on sets", but she was beaten by a "pretty good surfer".

"I've learned [this week] to have fun and it kind of doesn't matter if you lose - just always look forward to the next wave," she said.

"Hopefully I will come back stronger next time."

More than 50 of Australia's best and most promising surfers took part in the three-day competition, which began on Tuesday.

Oceanna was the sole South Coast representative to compete on Thursday's finals day after she beat Culburra Beach's Keira Buckpitt in a semi-final, while Port Kembla's Charli Hurst also reached the under-16s girls semi-finals.

Long Jetty's Milli Alport took out the under-16s girls class, beating Victorian Ellie Harrison in the final.

Quincy Symonds (Tweed Heads) secured the under-12s girls title with a solid win over Northern Beaches surfer Ruby Trew.

Port Stephens teen Mike Clayton-Brown claimed the under-16s boys silverware with victory over Queenslander Marlon Harrison in Thursday's decider.

Queensland's Braxon Holmstrom secured victory in a thrilling under-14s boys final against Swansea Heads' Dom Thomas.

Maroubra surfer Jake Feher pipped Fletcher Kelleher, of Freshwater, by just 0.47 points to claim the under-12s boys national title.