Any ideas?
Teakguard is good stuff, but requires the same number of coats as varnish - as other said - depends on what you want it to look like - gloss or satin or oil? Speaking of oil, be careful with linseed oil on wood that is exposed to high humidity - mildew and mold feed on the organics in linseed oil and can turn teak black. All the name-brand teak oils (and varnishes as well) include an anti-fungal agent to keep mildew under control. Good luck!