Hsiyu is long and narrow, shaped a bit like a seahorse. A big bridge connects its northern end to Paisha Island, while the southern tip looks across the water to Penghu Island and the county seat, Makung.
島形狹長，宛若海馬，北以跨海大橋與白沙島相接，南端與馬公相望，合抱成一個圓形的內海。