。
She can swim farther than I can.
Literal
She [topic-は] me [than-より] far [as far as-まで] can-swim.
遠くまで ('all the way to a distant point') uses 遠く — the adverbial form of 遠い ('far') — with the endpoint marker まで. Together they specify the spatial reach of the swimming. 泳げる is the potential form of 泳ぐ ('to swim') — for godan verbs, the potential is built by changing the final -u to -eru. Combined with より, the sentence draws a comparative claim about capacity. Common in athletic or adventure contexts where reach or endurance is being measured.