Lobb's water buttercup is an aquatic annual wildflower found floating and rooted in vernal pools or roadside ditches. The stout stems are horizontal or ascending and measure up to 100 cm long. The roots are fleshy, measuring up to 3 cm long and 3-5 mm thick. Two types of leaves may be observed. The submerged leaves are dissected into many needle-like segments while the floating leaves alternate along the stem and have slender to stout petioles from 1-5 cm long with blades 5-10 mm long and 2.5-5 mm wide. The blades are 3-parted with wide sinuses, the segments obcordate in shape or with 3 short rounded lobes. The leaf blades may have small purple blotches.
The small flowers have 5 petals and 5 sepals. The white to yellowish petals measure from 4-6 mm long. The sepals may have small purple blotches. The stamens number from 10-16.
Lobb's water buttercup is found in lowland vernal pools.
Lobb's water buttercup is found intermittently along the Pacific coast from Vancouver Island south to California, and inland along the Columbia River Gorge east to Wasco and Benton counties, Oregon.
In the Columbia River Gorge it may be found between the elevations of 100'-1400' from Troutdale, OR east to near the Klickitat River.