I've had the fog problems many times now, each time when it's hot and humid on land but the water is cool. Each time it's taken 50 minutes for the lens to unfog. Very frustrating.
I've tried silica gel sachets retreived from old packing boxes containing electronic gear, and I've been recommended and tried teabags - all useless - more fog, more heartache.
If it's humid topside and cool below, you need fresh desiccant. A sachet that's been left in the open for a couple of days is no good. Now I recharge them in the oven regularly and keep them in an airtight container right up to putting them in the housing. It works.