"Me mashed potatoes are goin' wild in me tummy" confessed Jane, the Yorkshire chanteuse who brings a dash of the Batley Working Men's Club to the passengers of the Galaxy, a floating leisure centre which is the subject of Christopher Terrill's The Cruise (BBC1, 8.00). Jane is very likeable, not only because she hides vodka in an Evian bottle in order to steady her nerves before curtain up or because she gets weepy when she calls her mum up on the telephone, but also because of the unstinting conviction with which she belts out cover-versions of Tina and Whitney hits.

Never mind that the front row is filled with wildly flailing children, never mind that half the audience are sleeping off the effects of the all-you-can eat buffet, like anacondas in Hawaiian shirts - in her heart she's top of the bill in Vegas. You need this almost deranged cheerfulness to work on a cruise ship, I would have thought - at least it appears to be a quality shared by all the other front-of-stage staff. The captain is permitted to look mildly bored as he mutters compass bearings from the bridge, but the rest of the staff are positive geysers of joviality - from the cruise hostess who says everything in a gleeful rising intonation to Scotty the DJ - a monster of compulsory fun.

Terrill is neither malicious or underhand about any of these characters but he doesn't forget where he is either - as Scotty pumped out his mantra of personal empowerment ( "Now I'm a success, I'm an excellent success") the camera stole a glance at the collage of snapshots on his cabin wall, lingering on an image of Scotty with a finger poked halfway up his nose. He's just a big kid, was the burden of this edit, but a harmless big kid for all that. If the staff give the impression that they are sailing on the good ship Prozac, many of the passengers act as if the trip is a cunning conspiracy to defraud them. This tendency was well represented by a doughty lady from Finchley ("My member of parliament used to be Mrs Thatcher", she told the hairdresser, in a tone that suggested the two women had more than a constituency in common). Her mantra was rather different to Scotty's though repeated with equal vigour: "I've been on 17 cruises... and I'm not happy".

You could tell she was though, because she could simultaneously enjoy the ship's facilities (which included waiter service for her teddy-bear) as well as the invigorating pursuit of a justified complaint. Her husband - a man you never saw in full because she was always standing between him and the camera - had wisely decided to adopt the Denis role of patient consort.

Cathy Elliott's Inside Story (BBC1, 9.30) film about schoolgirl mums began with a calculated shock - a montage of teenagers getting ready for a night out, choosing clothes and putting on make-up. Then, in a series of rapid cuts, three babies appeared in their arms. Spot the out-of-place object. What followed was similarly constructed, as if to ensure that the occasional lifting of your spirits would be followed at once by a jarring drop. So, just as you were allowing yourself to feel a twinge of hope about Rhonda (aged 15) and Andy (21) it was revealed that Rhonda's mother's boyfriend was on remand for assaulting Andy with a Stanley knife. And just as you'd absorbed that information you were told that Rhonda's mother was pregnant too, an uncle or aunt due to be born shortly after its niece.

The most hopeful story was that of Bonnie, a 25-year-old woman who had built a good career for herself and was now sending her 10-year-old daughter to private school in order to break the cycle. Elliott let you clutch at this straw for a long time before revealing, in the very last minutes, that Bonnie had "fallen" pregnant again by someone called Popeye. Rhonda finally nailed the lid shut on your optimism by announcing that Andy - the only male in the programme to have acted with anything like paternal responsibility - would have to move out soon, because she couldn't face the thought of living with him for the rest of her life.