It's Not Easy Being Green (BBC2 8.30pm) Shark (Five 10pm).

IT'S not easy being green. But having £750,000 to splash out on an eco-house makes it a whole lot easier. Tonight's documentary follows the Keenan family, from the Wirral, as they build a huge mock-Tudor house in the countryside. It even has six toilets.

To feel less guilty about their ostentatious display of wealth, the Keenans are making it an "eco home". It's a bit like "offsetting" long-haul flights. No one really knows if it makes any difference. No one really cares. But it makes you feel better.

The Keenans' eco-home includes a huge wind turbine in the back garden, and an underground water pump.

But don't worry, says Dick Strawbridge, the documentary's presenter: "All the principles they are following could work for us at home." You're right, Dick. I'm sure someone on the eighth floor of a tower block can follow the principle of a wind turbine in the back garden. And a water pump underground.

You get the impression, though, that the Keenans aren't bothered about saving the world. They just want something to talk about at the next dinner party.

"Nice house." "Thanks - it's an eco home." "Nice coffee." "Thanks - it's made from grey water cleaned by our eco-filter."

The Keenans have six toilets when one would do, and they import oak from France because it's cheaper. Think of the "wood miles" in that. Even Dick admits: "I don't think they are motivated to save the planet."

But it is very hard to dislike Russell, the head of the Keenans' household. I tried. The problem is his day job. He's a cancer specialist. When he's not trying to save the world, Russell treats young leukaemia patients.

I told you it's hard. He even paid for his first house by busking while a trainee doctor. Perhaps he could illuminate his eco-home with the light from his halo. Think of the carbon that would save.

The other family in It's Not Easy To Be Green are the Hunts, from Essex. Their goals are more modest.

Ethan, their young son, is allergic to everything. And I mean everything. I nodded off half way through the list, but it did include gluten and fish fingers. So the Hunts want to grow their own veg. Their garden is tiny, and allotments "are like gold dust".

Enter the BBC. They've had Ben Hunt's name on a waiting list "for months". Yeah right. I bet some poor fella in Essex has been waiting years to grow his own carrots. And then he's gazumped by Dick Strawbridge and the licence fee. It's Not Easy Being Green - unless you're with the BBC.

The show's only entertaining moment is Ben's lifeless reaction when Dick hands over the allotment. "This is it," Dick beams. "It's yours!" "Wow" says Ben, through closed teeth. It was like someone had force-fed Ethan a fish finger sandwich.

There is one big difference between Shark and It's Not Easy Being Green. Shark is worth watching.

Shark is not about sharks, thankfully, but about a lawyer called Sebastian Stark. Stark-Shark. Can you see what they've done?

It's another of those highly-unlikely, highly-enjoyable American dramas. James Woods stars as a former defence lawyer who becomes a prosecutor after one of his clients repeats the crime he was cleared of. He is smooth and sharp-tongued, but - refreshingly - not very good looking. I get jealous quite easily.

Stark soon tells anyone who will listen his three life rules. One: trial is war, second place is death. Two: truth is relative. Three: In a jury trial, there are only 12 opinions that matter. I think he's missing one. Four: Only use grey water pumped from an underground tank and always grow your own veg.

Poor Stark's dinner parties must be very dull. What does he find to talk about?