The Canal della Giudecca is the wide channel of water south of the main grouping of islands and north of the long La Giudecca island at the bottom of the map.  
 

In a Gondola (Jane de Glehn) 
1904 

To find his scenes in and around Venice, Sargent often paints directly from gondolas taking a page right out of Claude Monet's handbook for painting in plein air. Edouard Manet had captured Claude doing this with his wife in 1874 (thumbnail right).  As Sargent grows more and more tired with the limits of portraiture, we find him embracing these ideals in his watercolors and his paintings in Venice are magnificent  "impressions" of a time, for us now, so long ago gone. 

This would become John's favorite modus operandi. Often it was the Curtises who would let them use their gondola from the Palazzo Barbaro where he was staying.

The two occupants that we see in Sargent's painting could very well be Jane and Wilfrid de Glehn who often traveled with him. In another time, Wilfrid returned the complement by painting Sargent with his wife in another part of the city (thumbnail below).

Wilfrid de Glehn

Sargent and Jane de Glehn Sketching in a Gondola 
 

Claude Monet   Grand Canal, Venice   1908   Claude Monet  Oil on canvas  Museum of Fine Arts,  Boston  Bequest of Alexander Cochrane

It's interesting that four years after Sargent's Sketching on the Giudecca, it would be Monet that would follow in Sargent's footsteps, when Monet makes his trip to Venice.

Venetian Fishing Boats sit anchored with mooring lines like spider webs crisscrossing between the craft to keep them apart. Sargent takes his Gondola with his friends and they row to the middle where they tie up between boats, fastening their own lines -- bow and stern -- to the heavy hemp ropes of the mooring lines.  There is some  shifting of seats, adjusting the canopy for shade and moving paint-boad to the edge of the gondola.  The fisihing boats resting on the surface sit like sleeping geese, the smell of their catch  -- now at market -- on the hanging nets and the sails that are drying in the sun.  

Sargent moves quickly with sketches in pencil, sensing the the composition as a fisherman senses time and place to drop nets. He leans over and scoops a handful of water from the canal, wets his paper, then swiftly moves with sponge applying big washes  of color . . . the painting begins to emerge. 
 

Notes:

Exhibitions

• See the Map of Venice
• See the year in review  1904