Highly efficient single-walled carbon nanotube (SWNT) growth from Fe-Mo nanoparticle catalysts made by colloidal synthesis is demonstrated by water-assisted chemical vapor deposition. In a 10 min. growth time, SWNT forests with heights up to 1.5 mm were synthesized possessing a 2.8 nm average diameter, carbon purity above 99.99%, and Brunauer-Emmett-Teller (BET) surface area of 1200 ml/g, which rivals SWNTs grown from sputtered Fe thin films. Realization of high efficiency SWNT growth using catalysts prepared by economical and scalable wet processes opens up a cost-effective route toward the mass'production of SWNT forests.