Make that a sea sponge, in the case of Frans Masereel.

Masereel lived in Ghent, Paris, Geneva and Nice, but the sea, where he was born, came back in his work for the rest of his life. He lived with his parents in a townhouse on the promenade of Blankenberge until, coincidentally, the age of five.

One of the world's best (and certainly its most prolific) artists of woodcut graphics, Masereel produced more than a thousand of them before his death in the early 1970s. Although he is best known for his socially conscious and anti-war themes, many of which he produced for pacifist magazines, Blankenberge's current exhibition of his work is titled Masereel and the Sea. Not only was there no shortage of woodcut graphics to choose from, the show features the Flemish artist's lesser-known watercolours and oil paintings, of which he also produced more than 1,000 in his lifetime.

Woodcut graphics are not an overwhelmingly popular genre of art, but they are breathtaking in the simplicity of their stark contrasts, which belie a complexity in craftsmanship. An image is cut into wood, like a relief, and the raised portion is covered with ink. The finished woodcut is pressed onto paper or other material, leaving behind a printed image. The exhibition includes a piece of wood used for a woodcut so you can understand the process better. Peek around to the back - Masereel used both sides.

Educated at Ghent's Academy of Fine Arts, Masereel relocated to Paris in 1911, where he made his first woodcuts. He was 25 when the First World War broke out, and he fled to Geneva, from where he illustrated the cover of the pacifist Le Feuille every single day for three years. That work, plus similar illustrations for Les Tablettes, made him a graphic sensation, and he published many of his woodcut albums during this period - books that told a narrative story using only woodcut graphic images.

A few years after returning to France, Masereel bought a rickety house on a rocky slope in the remote fishing village of Equihen, where he and his wife spent every summer. The hundreds of sea-themed pieces are not the artist's best-known work in woodcuts, and yet they define a number of his preoccupations and pop up in many of his books.

A number of the exhibition's drawings and woodcuts emphasise the wistfulness that people feel standing on the shore staring out at boats on a seemingly endless horizon. In some, such as the delicate "Wavebreaker" - which Blankenberge Cultural Centre is using on its promotional materials, despite the diminutive size of the original - men take tentative steps towards its mysterious depths.

In the show's most intriguing (and larger) woodcuts, the sea and the cities on its shores seem to negotiate an uneasy relationship, neither really trusting the other. This is most often depicted with Masereel's generous use of sirens - the sometimes noble, sometimes dangerous women of the ocean. In 1955's "Poor Siren", one has been pulled from the water, her hand caught in the massive chain of a ship's anchor, her fish tail dangling helplessly in the night air. Men gather ominously onshore. Conversely, "Poor Fisherman", made a few years later, finds larger-than-life sirens towering over a shipwreck, seeking out their victims.

The epitome of this theme has to be "The Wave", one of the exhibition highlights, in which a giant tidal wave carries off an entire city, skyscrapers bobbing in its wake.

But occasionally the city/sea dichotomy produces something playful. "The Aquarium", from 1960, shows what is happening in the harbour of a large city. The marvellous and fantastical - almost colourful - creatures are having the time of their lives just beyond the view of those existing above.

In the 1930s, Masereel began a life-long affair with a younger woman, which you could guess from the turn his work takes even if you didn't know it. Since the 1920s, there were the ever-present sirens, but in the next decade and beyond, there are curvy nudes, lounging on the beach, splashing in the water. In two striking woodcuts, they are wading out to sea, but the sea is illustrated by such fine dark lines, it could appear simply as darkness - figures wandering into the void.

These works, from the 1950s and '70s, appear to be a sign that Masereel has come somewhat to terms with his relationship with women. In much of his work from the 1920s, women are often subjects of stark voyeurism, naked worshippers of powerful men or prostitutes, such as in 1928's "The Catch", a disturbing portrait in which it is unclear what role the woman is playing in her own victimisation.

Masereel's oil paintings fall into landscapes - which are generally clichéd - and people, which are strong and bold, the paint smeared on thickly with a palette knife. Masereel once said that his earliest memory of childhood was running about with an old sailor in Blankenberge who sported a big, gold earring. This series of oils reflects that sort square-jawed, leathery-skinned worker, with whom he again became familiar in Equihen. But rather than rough and tough, their expressions seem almost fragile, staring down a pint glass, holding their wives like they may never see them again.

As a bit of a bonus gift, the exhibition throws in a few of Masereel's woodcut masterpieces that are not part of his sea images. You'll find "The Boxer", "Spleen" and, my favourite, "The Kiss", in which two people act out the title leaning across a busy city street from several stories up. A bit further, however, you find the sea version of "The Kiss": in "Somebody Loves Me", two people lean across an ocean from different lands, managing to meet in-between.

It's poignant in its romance, but I'm even more swept away by "The Adventure", where a young man stands on a pier in front of a sea with a shining lighthouse, a ship full of masts pulling alongside, a sea creature surfacing, a siren floating nearby. An airplane flies among bubbly round clouds, stars twinkle, city lights shine. The man watches it all blaze around him like a show of fireworks - every kid's imagination of what the world holds.

Masereel and the Sea
Until 4 October
Casino Blankenberge

www.blankenberge.be

Frans Masereel Centre

Kasterlee is home to this centre for the study and support of graphic arts. A permanent exhibition of the work of Frans Masereel is open to the public.

www.fransmasereelcentrum.be