After three ruined hoops I figured out why my first thread painting attempts looked flat. The trick with a paddling bird is the split above-and-below view, and you have to treat those as two totally different jobs. Above the waterline it's all about feather direction, short rows of long and short stitch working from the head back, one strand only. Two strands and the texture dies immediately.
The submerged part is where most people panic. Don't. Keep your stitches loose and slightly wavy, and drop the thread tension way down compared to the top half. Then come back in with a few single straight stitches in white or pale blue scattering around the body to read as bubbles and ripples. Weirdly that tiny detail sells the whole piece.
Order of work matters too. Background fabric and water first, then the body, feet last so the orange webbed bits sit proud of everything. Outline key edges in split stitch before filling or your edges go soft. And hoop up on something plain and cool toned, anything busy fights with the stitching. My first attempt on a patterned fabric looked like a smudged ghost bird and I nearly quit. Second hoop, plain fabric, night and day.