When I feel like eating fish in Edinburgh, my first instinct is to head for Ondine.

How many times have I eaten there? I have lost track, and each meal has been as memorable as the next.

At Ondine you are always served the finest, freshest, most thoughtfully sourced seafood these isles produce.

You also know that this prime haul will be cooked with a spirit of adventure that is tempered by culinary literacy. We Scots can be too timid and conservative in our approach to fish.

As chef-proprietor Roy Brett once said: "We have fantastic raw ingredients in Scotland, but sometimes we have to take them on a wee world tour."

So like a mussel clamped on to a rope, it takes a lot to prise me out of Ondine, but I was intrigued by C-Shack. For starters it has a plausible location, right down on the harbour at Newhaven.

The Forth estuary glimmers just across the road, small fishing boats bob up and down on choppy waves, and there's something about a vista of sea (or river) that makes you hopeful about being served really fresh fish.

But you can't take such visual cues for granted. How many paellas are served up each day in coastal Spain that contain frozen Scottish langoustines? Wherever you go in the world now fresh seafood comes at a premium, and isn't always quite what it seems.

In Italy, restaurateurs must, by law, put an asterisk on the menu next to any dish that contains frozen fish. Elsewhere there's no such transparency.

Frozen seafood sold as fresh is less of an issue in Scotland, but we do serve up our fair share of "fresh" fish that has lost its just-netted sparkle.

C-Shack also appealed because the chef is Thai, and Thais have all manner of exciting treatments for seafood. And as it transpired, C-Shack has a chef whose gastronomic knowledge also ranges further afield.

For instance, C-Shack does a ceviche of the day, a Latin American technique where raw fish is "cooked" in citrus juice.

Ours was made with thin slices of scallop and its symphony of clean, clear Thai flavours - fresh coriander, fish sauce, lime and more - really woke up the salivary glands.

Salt and pepper squid in its delicate, crisp tempura-light batter was up to Ondine standard, flanked by a bright chili sauce, but not that sickly, sweet, starchy stuff that comes in jars.

Perversely, for C-Shack is a modestly kitted-out little eating place, it specialises in lobster. That's not as nutty as it may sound; apparently, there's a local lobster fisherman on the harbour who merely walks them across the road from the boat, claws clamped with stout rubber bands, naturally.

Judging from its well-toned fleshiness, our lobster was ultra-fresh, but I couldn't really taste the crustacean for the domineering garlic butter that bullied it.

Even as someone who likes strong flavours, I'm not convinced that lobster and garlic are the perfect twosome. (It's hard to beat Andrew Fairlie's approach at Gleneagles: herb butter, cut with lime, on lobster lightly smoked in the shell.)

More to my taste at C-Shack was the tamarind and coconut monkfish, a creamy pink curry that came with appetite-whetting saffron rice, aromatic with star anise and cardamom, although I could have done with more monkfish instead of the tropical tiger prawns, which taste of very little and certainly don't come from Scottish waters.

The sweet offerings at C-Shack show a characteristically Thai delicacy. Those round, firm imported plums are unrewarding to eat raw, but here, three plump purple halves, adeptly poached and spiced, strewn with a home-made granola, embellished with an emollient egg custard, and topped with barely sweet yogurt sorbet, looked and tasted great.

Chocolate orange brownie with peanut butter ice cream, although chunkier to look at, was every bit as good to eat.

C-Shack certainly adds to Newhaven's reputation as the place to eat seafood, but it does need to sort out its kitchen extractor if diners are not to come out smelling like chips; a teething problem that's easy to remedy.