Humboldt Bay, the only deep water port between San Francisco and Coos Bay, Oregon, is located on the coast at the midpoint of the county.
The smaller rivers include: Redwood Creek, significant due to amount of its flow; the Van Duzen; the Eel River syncline group composed of the South Fork, the North Fork, and the Salt River; the Mattole, Salmon, Elk, Bear, and Little rivers.