San Francisco Bay's only private island is on sale for $25 million — but there's a catch

• San Francisco Bay's only private island is on the market for $25 million
• Red Rock Island lacks basic infrastructure like power and running water.

San Francisco Bay's only private island is on the market for $25 million — but there's no electricity or running water, reported The Wall Street Journal.

Red Rock Island is six acres in size and only accessible by boat or helicopter, the island's listing agent Chris Lim told WSJ.

Photos of the island show a mound with reddish soil dotted with foliage and surrounded by water. The island is a mile from the Richmond-San Rafael Bridge, located on Interstate 580 between Contra Costa and Marin counties.

"This is about collectible real estate," Lim, president of Christie's International Real Estate, said.

The island lacks any infrastructure — there's no power, running water, or shelter, Lim told WSJ, noting that desalination, solar panels, and satellites can be put in.

Brock Durning, the current owner, inherited the island from his father, who purchased it from his business partner for less than $50,000 at the time, Durning said.

Durning's father had previously planned to convert the island into a 20-story hotel, casino, and yacht harbor in the 1960s, the San Francisco Chronicle reported in November 2014. But the plan never materialized following a public outcry, per the report.

Durning told WSJ he's putting the island on sale as he lives in Alaska and hasn't visited in several years.

"There's no reason to hold on to it," Durning said.

The island has been put up for sale several times in recent years for between $5 million and $22 million, Durning told WSJ. In September 2015, the island's asking price was halved from $10 million to $5 million, before being raised to $25 million this month.

Several other private islands have been put up for sale in recent months. In September, a private island in Solano County, California was put on the market for $75 million. And in August, a private island in Maine with a cottage and lighthouse was listed for $400,000.

Lim did not immediately respond to a request for comment sent outside office hours.