Zippy Fish has played a key role as Sydney fought off a spirited challenge from Fremantle to win by 25 points and stay undefeated in the AFLW season.

Flashy half-back Fish kicked her career-first goal as the Swans made it four wins on the trot with a 9.8 (62) to 6.7 (37) result at Henson Park on Sunday.

The Swans kicked four goals to none in the third quarter after an evenly-matched opening half to set up their longest winning streak in the AFLW.

Fish, who had 11 touches and laid six tackles, combined well with Swans captain Chloe Molloy (two goals) in attack, while ball magnet Laura Gardiner led the way with 35 possessions.

Exciting first-year player Fish, wearing AFL legend Lance 'Buddy' Franklin's No.23 guernsey, had gifted Sydney a one-point lead at quarter-time with her first goal.

It was a fitting start for Western Australian product Fish - a Larrakia, Noongar, Wongi and Wirangu woman - to mark Indigenous round.

The Swans could only build their advantage to three points despite more magic from captain Molloy.

Molloy fought off two Fremantle defenders at the boundary line and got the ball home with a soccer kick from the tightest of angles.

The Dockers had opportunities to take the lead after a Tunisha Kikoak goal but the visitors could only add five behinds.

Sydney came out firing after halftime and finally broke away by 31 points after slamming through four unanswered goals.

Fish had flaunted her pace to burn competition heavyweight Hayley Miller down the corridor and set up Molloy's second goal.

Gabrielle Biedenweg-Webster hit the scoreboard for Fremantle in the final quarter but it was too late.

Mim Strom was massive for the Dockers with 15 hitouts, 24 touches and 11 clearances against Swans counterpart Ally Morphett (13 hitouts).

The 23-year-old Dockers ruck was well-supported by Kiara Bowers, who had 22 disposals.