Ridge and buried channel waveguides (BCWs) made using plasma-enhanced chemical vapor deposition were fabricated and tested after being subjected to long 85°C water baths. The water bath was used to investigate the effects of any water absorption in the ridge and BCWs. Optical mode spreading and power throughput were measured over a period of three weeks. The ridge waveguides quickly absorbed water within the critical guiding portion of the waveguide. This caused a nonuniformity in the refractive index profile, leading to poor modal confinement after only seven days. The BCWs possessed a low index top cladding layer of , which caused an increase in the longevity of the waveguides, and after 21 days, the BCW samples still maintained throughput, much higher than the ridge waveguides, which had a throughput under 5%.