Remember seeing this on George Clarke's amazing spaces tv series, UK. Underwater garden/greenhouse, or as they call it Nemos Garden.
Yes herbs grown in 6 biospheres weighted down with air inside, under the water off the coast of Italy.
Indeed biospheres as reading this link suggests that they're even becoming havens for marine life.
From the same link they describe the spheres benefits,
'The balloon-like biospheres take advantage of the sea's natural properties to grow plants. The underwater temperatures are constant, and the shape of the greenhouses allows for water to constantly evaporate and replenish the plants. What's more, the high amounts of carbon dioxide act like steroids for the plants, making them grow at very rapid rates.'
Here's Nemos garden description,
'Agriculture represents 70% of freshwater use worldwide: water management is needed in most regions of the world where rainfall is insufficient or variable. Increasing pressure is being placed on water resources by industry and urban areas, meaning that water scarcity is increasing and agriculture is facing the challenge of producing food with reduced water resources.'
This idea would work for areas with difficult climates for growing. I like the innovation of growing in different terrain, and that the carbon dioxide accelerates, or at least is at a high level to feed their growth.
They have a live webcam but what I like is their live data feed of each pod.