When you need a bucket-full of seawater, make sure you have a longish lanyard. Tie it to the boat because under way the pull can be considerable. To make sure of a decent fill every time, don’t just drop it in and hope for the best. Instead, gently lob the bucket rim-down into the sea and tip it round so it’s open to your direction of travel. It can bring you up with a jerk if you aren’t careful, but that’s where the skill comes in. Flicking it out just as the pull comes on is the mark of a real seaman!
Buy a quality bucket from your local builder’s merchant, and choose the smallest. Failing this, try the chandlery, but never be tempted by lightweight plastic rubbish fit only for the kitchen. Go for heavy rubber or a nice canvas one. A good bucket is a friend for life.