I wouldn't like to paddle wearing that, it would act as a sail.
As a shore based group shelter i would suggest a Bothy bag, they are very popular here with the outdoor set. It is almost standard kit for groups that venture into the mountains. Ideal for caners and kayaks to. Mountain rescue use them when working on casualties.
Lightweight and windproof, they come in sizes from two man to 16 man. And man they worm up quick when there is a group sat under one.
I use mine for lunch stops and emergency use, a great bit of kit.
http://www.terra-nova.co.uk/Product_Type/Tents/Bivi__Bothy_Bagshttp://www.lifesystems.co.uk/psec/mountain_survival/thermal_protection.htmhttp://www.vango.co.uk/products/tentsinfo.aspx?productid=31&modelid=27&id=20http://www.outdoordesigns.co.uk/products_shelters.htmlSix scouts inside my 4 man bothy bag on a cold morning, they were soon complaining how warm they were getting.