This white sandy beach seems like a bit of an anomaly on the southwestern coast of the Ring of Kerry. Aerial images don't show much in the way of beaches, even small ones, along this section of rocky coastline, yet this bay has a really nice one. Typically, beaches need both a source of sand and a place for it to accumulate. No sediment, or a coast so steep that sand is lost offshore, prevents beaches from forming.
The sediment here may have been delivered by the stream at the head of the bay. This assumes that the stream valley yields a reasonable amount of sand, perhaps from glacial deposits. Another option, not necessarily exclusive of the first, is that glacial drift was deposited in the lower valley or the bay and waves have redistributed it directly.
In either case, a broad, relatively shallow bay would have fairly little accommodation space, and a modest amount of sand would accumulate fairly rapidly. And wave action would tend to trap the sand within the bay.
The main feature is a broad spit, backed by dunes, but the beach is strung out along the northern shore behind a series of rocky ledges. And there is a tombolo at the west end linking the beach to Abbey Island.