The vessel was caught on a member of public’s phone at around 12.37pm on Sunday in the Scotforth area.
The 200 year old waterway has a 4mph limit to protect the structure and its users.
The wash from a speeding boat can hurt wildlife, damage the canal bank, and push other boats - causing a serious accident if a boater is, for example, making a hot meal or drink.
Witness Andrew Lucas, from Lancaster, filmed the boaters.
He said: “I estimate he was doing about 25/30mph when passing us and he had slowed at least 10mph before I shot this video and sped up again after going through the bridge.
“He must have passed a canoeist about 2 minutes before he reached us - if the canoeist had been hit he would have been killed.
“Unfortunately, the wake covered the name of the boat.
"After we had seen it, my partner and I asked other boaters if they had seen them, and many were reporting they had received abuse.
"Twice people on their boats had been making a hot drink and almost ended up with scalding liquid over them.
" It was really awful. They quite clearly had no regard for the safety of other people and wildlife.
“We also had reports of abuse to other boat owners, and that they were drinking Fosters.”
Another boater confirmed seeing two dead ducks, though it isn’t clear if the incidents are linked.
A kayak user posted in the group about his encounter with the two men, writing: “I heard them and pulled right. Gave me some s**t but I ignored them.”
The footage was tweeted to the Canal and River Trust (CRT), which looks after the canal, and Lancashire Police.
If anyone has information call 101 or the CRT on 0303 040 4040.
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