In a post on her blog, the Rosemary's Baby star reveals there are over 800 tunnels along the border between the Gaza Strip and Egypt - and one collapsed on Sunday as aid workers were bringing in supplies.
Farrow writes, "While I was in Gaza, one tunnel worker, a child, was killed and seven were injured during an Israeli bombing raid. The 1.5 million people living in Gaza depend on hundreds of tunnels beneath the border to get fuel and other products, since Gaza has been sealed off after the Hamas takeover in June 2007.
"Israeli bombings are frequent and more than 130 Palestinians, many of them children, have been killed while working in the tunnels."
And the celebrity activist's thoughts are with those suffering in Gaza, who are also without fresh water.
She adds, "Most of Gaza water is unsuitable for drinking... The daily quota of water for each person in Gaza is 80 liters, half of the W.H.O (World Health Organisation) minimum standard. The 1.5 million people of the coastal strip rely on one aquifer as their sole source of water.
"However, the sea water has blended with the underground water, making it salty. Since the sewage plant was also bombed, raw sewage flows into the sea."
Israel has imposed a complete closure on Gaza since 2007 and the rebuilding of sewage and water treatment stations is impossible due to the lack of building materials and spare parts. Last week, Amnesty International accused Israel of depriving Palestinians in Gaza and the West Bank of water.