Green’s Dictionary of Slang

skeg n.¹

(Aus.) a surfer.

1984		Tracks (Aus.) Aug. 3: I doubt all you skegs with your prunehead girlfriends have ever been further west than the Caringbah Inn, so what do you know about westies? [Moore 1993].
2001		Sun Herald (Sydney), 19 Aug. 15: They tell the story of a neighbourhood under siege, divided between ‘skips’ (Australians of Caucasian appearance) and ‘lebs’ (Australians of Middle Eastern appearance). […] ‘I hate the fact that simply because I have fair skin, fairly fair hair and look like a “skip” or “skeg” or “surfie” that I’m safe at the beach only.’.

In compounds

skeghead (n.)

1. (Aus.) an obsessive surfer.

1991

Age (Melbourne) 10 Feb. 55/2: Skegheads like Healy [...] are very much at home on the high seas.

2. see scaghead under scag n.²