There are two main types of boat fishing rod used in the Bristol Channel area depending if you are fishing down tide or up tide from the boat . You can use a standard 15-20lb boat rod to fish downtide or a 6-10oz uptide rod for fishing uptide .These two rod types offer you advantages in each case.  Uptide rods are often longer, 8 - 10 feet with a softer tip end that allows you to cast better from the boat and also give better bite detection. Due to the confines of casting from a boat it's recommended only experienced anglers use this method.   Downtiding is usually done with shorter stronger rods,5-8ft, which don't require casting from the boat,but instead are used to lower the weight off the boat allowing the current to drift the end rig  downtide away from the boat until the weight hits the sea bed. This is the method better suited for the novice boat  angler as the rod and reel are easier to control but can still produce good results.
The "Scare" Area
When at anchor in shallow water a boat and the people on it can create  noise – from waves slapping the hull,the anchor rope in the tide as well as simple things such as anglers making a noise when moving around on the deck. It is believed that these noises, magnified in the sea can scare fish away from a feeding directly beneath an anchored boat. So when using either method of fishing make sure your bait is far enough away from the boat to be outside the "scare" area.