The Pigeon Holes are a sandstone bluff on the South Arm peninsula, north of the township, where wind and water have eroded the rock into a honeycomb of hollows that the Marine Life Network guide likens to a pigeon loft. Underwater, the guide describes a shallow reef in about 3 m with a good variety of fish within easy snorkelling depths, including school fish, stingrays and flathead, along with sponges and a seaweed garden. It rates the site as suitable for beginners with minimal hazards.

The sandstone continues below the waterline as ledges and small overhangs, where sponges and ascidians grow and small fish shelter, and the weed garden beyond gives way to sand where rays and flathead lie. Because it is so shallow, the site is best treated as a snorkel or a relaxed, long scuba dive for new divers, and it is ideal for families with a boat. The western side of the South Arm peninsula is sheltered from easterly weather, and the site is a short hop from the South Arm ramp.

Visibility varies with the Derwent's condition. The eroded bluff is also worth seeing from the water for its own sake. It is an ideal first open-water experience for children or nervous snorkellers, and a pleasant surface-interval stop between deeper boat dives at the Iron Pot or Betsey Island.

On a calm, sunny day the shallow sandstone reflects plenty of light, and even with modest visibility the fish are easy to see. Bring a small boat anchor suitable for sand and keep well clear of the fragile sponges on the ledges.

South Arm is about 35 km (40 minutes) south-east of Hobart: cross the Tasman Bridge, follow the South Arm Highway (B33) through Rokeby and Lauderdale to South Arm. The main boat ramp is at South Arm (Blessington Street/Harbour area) with trailer parking and toilets; Lauderdale (Doran's Road) is an alternative ramp further north. The Marine Life Network guide lists this as a boat dive from the South Arm ramp; the bluff is a short run north along the shore, about 5-10 minutes.

Anchor in sand off the bluff.

The South Arm peninsula and Iron Pot sit at the junction of the Derwent and Storm Bay. Western shores and the lee sides of the islands are sheltered from easterlies; eastern and southern faces are exposed to southerly swell rolling in from Storm Bay. Strong southerly winds and swell close the exposed sites; northerly and light westerly winds give the best conditions.

Visibility varies widely, from 3 m after Derwent floods to 15 m in clear marine water after a dry spell and a flood tide. Afternoon sea breezes can make the boat ride back choppy.

Anchor off the bluff, snorkel or dive along the base of the sandstone at 2-3 m, then drift out over the weed garden and sand looking for rays and flathead.

No regular operator; private boats and club snorkel outings from South Arm.