I too suffer with extremely frizzy hair. My Mum is a hairdresser so I've tried product after product (Paul Mitchell, Tigi, Frizz Ease, Aussie.....shampoos, conditioners, serums, mousse, sprays etc etc) to no avail. The only way I can keep my hair under control when I'm abroad is to keep it up in a scrunchie.
I shower in the morning and when rinsing my hair I leave a small residue of conditioner behind, this helps when it comes to the evening and time to wash it again after spending the day swimming, snorkelling and sunbathing! I then leave it in a scrunchie all day otherwise it soon becomes a straw-like mess.
I wash it again in the evening then back up it goes while still damp.
Straighteners are ineffective on my hair in very hot and/or humid weather. Blow-drying actually makes it worse!