| Not the best photo but my first aquatic leaf beetle (subfamily Donaciinae) which typically have strongly enlarged femora. The femora are the third segment of the leg (counting from the base), situated between the trochanter and the tibia. The larvae are aquatic and attached to host stems or roots; adults are found on vegetation bordering standing water. Interestingly, the larvae tap the submerged stems of host plants for oxygen and food.
bug guide (this photo):