in fairness I think people answering re wildfowling are answering at cross purposes as the thread has taken a tangent. Your first post.
Is incorrect. It is not illegal to shoot anything alive from a motor vessel at all.
Here is the legislation governing the activity...
And I found some guidance in the BASC website that puts it in simpler terms.
B Can I chase Canada geese on water in my boat? This depends on whether the boat is under power or not. If an engine is being used, then this would be an offence under Read more…
basc.org.uk
You can shoot wildfowl from a motor boat perfectly legally in the UK. You cannot use the engine in direct pursuit of the wildfowl.
I.e. If the boat is stationary and the engine is off, or if the boat is at anchor, pushed into a dry creek etc etc. You are acting legally.
Perhaps you ought to study the matter in more detail before posting on a subject that you know less than the asker?