These two small islands are just off the main Santa Cruz island, so are popular for day trips from Puerto Ayora. If you can avoid peak times though, there is plenty to see in a small space. You can only land on South Plaza, but boats anchor between the two islands.
See the Galapagos wildlife page for information on the flora and fauna of the islands.
There is a dry landing on a concrete pontoon along a rocky shore with sea lions, marine iguanas', sally lightfoot crabs and lava herons. A short path leads past prickly pear cacti and land iguanas up to some impressive cliffs on the other side of the island. Here you can admire numerous swallow tailed gulls all around - landing, taking off and swooping overhead.