Tom Sutcliffe: Water, water, everywhere at the Royal Academy's Sargent and the Sea exhibition

The Royal Academy's Sargent and the Sea exhibition has to be one of the nerdiest shows I've attended for years. I don't mean this to be a critical remark – or at least not entirely. There's a place for nerdiness in our understanding of visual art and, from time to time, it's surely right that the Royal Academy is that place. If mildly-obsessional scholarship is to be exercised anywhere then it should be here – or at the Courtauld or the National Gallery say. They know, for one thing, that they have a loyal audience who will be interested in the footnotes of a great artistic career. Even taking that into account though, Sargent and the Sea might be regarded as a special-interest affair – focusing as it does on just a few years of an artist's apprenticeship and then further narrowing down the focus to paintings and drawings of the sea. It's not even as if Sargent is famous as a marine artist, either – in which case this close scrutiny could be regarded as a tributary to the mainstream. It's just a phase he went through. I suppose they felt it would be alright because they had "sea" in the title – and that felt appropriately summery.

To be honest Sargent and the Beach would have been more accurate as a title – or Sargent and the Dockside. Because, although the rubric for the exhibition does suggest here and there that it's nature that Sargent is interested in, the truth is that you more often find him directing his attention at the sea's peripherals rather than the thing itself. There are numerous sketches of fishing smacks and lighters, of the details of rigging and pulley blocks. There are lovely, fluid line drawings of sailors hauling on their oars or pulling at ropes and fisherwomen walking down to the shoreline to collect oysters. There are sun-blasted canvasses of Capri beaches and the kind of study of pre-pubescent Italian boys which would, these days, earn Sargent a visit from the Vice Squad or a spluttering editorial in the Daily Mail. But, given the title, there's a striking lack of seawater.

It's there, of course – transparent and turquoise in a painting of an Italian beach and pooled in reflective puddles in the large painting "En Route Pour la Pêche", which helped establish Sargent's reputation in the Paris Salon (and whose painstaking creation is fascinatingly detailed here). But there are fewer pictures than you might expect in which the sea is the whole point of the thing, rather than a helpful occasion for people to take their clothes off or the location for some nicely fiddly bits of nautical gear. And – though this might be just prejudice on my part – it seems to be quite dry sea too, less a liquid element or something that threatens immersion, than an intriguing plane of colour which does interesting things to the light.

There is one huge, rescuing, exception though – a painting in which the sea doesn't lap gently at a Mediterranean beach or slop in a placidly disciplined way between the stone walls of a quay, but is primally overwhelming. It's called "Atlantic Storm", and it records a mid-ocean tempest Sargent experienced returning to Europe from America on the SS Algeria.

In this picture there's almost nothing but sea – a huge rising swell down which the liner from which the ocean is seen has just slid. A wake of pale blue foam rises over the hill of the wave and disappears into the trough behind. In the distance, despite the irregularity of the waves nearby, the horizon line is flat – a geometry that tells you this unnerving turbulence extends as far as you can see... and slightly to the left of the image the spray whipping from the peak of the wave tells you how hard the wind is blowing. In the company of the other pictures – sedate, moored up, sun-struck – it is, rather literally, a gale of fresh air, heaving with energy and a threat which is somehow emphasised by the blue sky and sunshine. At any moment, you feel, you could slip down the sloping deck and be lost. Life is not a beach and this – most definitely – is not a nerd's painting.

The star is terrible, but the show is great

You might think that great comic timing and acting ability were indispensable for a successful sit-com but Simon Amstell's forthcoming comedy Grandma's House suggests that isn't necessarily so. A Curb Your Enthusiasm-inspired series about a character called Simon, who has just given up hosting a successful television pop quiz to pursue other projects, Grandma's House is mostly concerned with Simon's interaction with the various members of his family – including his doting and pushy mother (played by Rebecca Front), his grandfather (the late Geoffrey Hutchings) and his mother's ghastly boyfriend – a cliché-spouting hail-fellow type played by James Smith, who was the put-upon Glenn in The Thick of It. They are all excellent. Amstell, to put it very mildly, is not. In fact he's startlingly inept – his features fixed in a embarrassed half-smile throughout, as if he can hardly bear to be in front of the camera. A speaking clock would probably give a more nuanced performance – something which is even more conspicuous given the subtlety of the acting all around him. It's a bit like framing a three-year old's daubed painting of Daddy in a priceless Renaissance gilt frame. And yet Grandma's House is very good and very funny. It's beautifully written and tartly excessive in just the right way. It even finds room for real feelings about family life, some of them involving the strange, wooden marionette at its centre. I don't know whether to recommend it because it's so good or he's so terrible – but, either way, it's something to see.

Spare me the blackboard jungle

I generally brace myself when I see a lecture hall in a movie, since it's usually a sign that you're a) about to have a large chunk of undisguised exposition or b) that you'll soon be writhing in embarrassment at Hollywood's notion of academic discourse. It isn't always terrible, of course. I quite liked the scene in Good Will Hunting where Matt Damon's janitor completes a problem that has stumped the university's top mathematicians, but only because it was so cheesy and everything happened after-hours. Far more typical are scenes like those at the beginning of Lions for Lambs, where Robert Redford's professor clunkily lays out the film's dilemma in a way that even a first-year philosophy student would find unimpressive. I tensed even more when Michael Caine appeared in a lecture theatre in Christopher Nolan's Inception, because if ever a film could legitimately claim the need for some clunky exposition, it is this one. And yet what could exposition do other than expose the underlying implausibility of the thing? Full marks to Nolan, anyway, for resisting the powerful temptation to sketch out the mechanics of his fantasy on the blackboard, instead leaving us floundering as helplessly as we had been before. (Out of curiosity, can anyone name a movie lecture scene that isn't intellectually risible?)

t.sutcliffe@independent.co.uk