It took me half an hour on my sewing machine. It weighs 100 grams, and measures about 10x15x3 cm when packed together.
Parts of the coast are very exposed, and landing may be impossible. We need to do lots of long open water crossings also. The sea anchor may be handy for taking breaks - rafted together - on open water far from shore. It will ensure that you're not blown back where you came from. It may be a life saving device also, if you are drifting helplessly from shore, for some reason unable to paddle. Hopefully we will not need the sea anchor for this - rather for having pleasant lunch breaks on the sea without drifting too much!