High Ref chilepepper

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According to RAW, shallow water is difficult terrain, costing two squares of movement to move into a square with shallow water.

Shallow Pool

If a square contains a shallow pool, it has roughly 1 foot of standing water. It costs 2 squares of movement to move into a square with a shallow pool, and the DC of Tumble checks in such squares increases by 2.
According to the map text (specific trumps general) you can wade through the water at half speed.

Since he isn't wading through the water, the map text doesn't apply. Since shallow water doesn't reduce movement, by RAW, it has no effect on jumping distance. His jump check is based on his regular movement.