In reply to dollydog:
> suit weighs 490 grams(0.4 lbs)
One pound avoirdupois is 454g. Whatever, it's still very light...
But then it's described as metallised polythene. And the wrapper says 'remove before entering water', and shows velcro fastenings, so the suit won't be watertight (I suspect it will fill with water if worn in the water, putting you in danger...) I suspect this is intended as protection against wind chill, so, for the suggested application of winter survival, a possibility. But a bag might do just as well, and be cheaper, and allow you to retain the heat from limbs better than individual legs and sleeves (cf mitts vs gloves).
The Ocean Safety website gives scant details, but says it weighs 0.2kg.