I have dove for over 50 years. I even spent some time commercial diving. For 28 years I carried all my gear on my commercial fishing vessels. I only used the gear once in those years to remove a lead line from my shaft after limping into a harbour. I broke three large knives cutting the line out, finally going to a hacksaw to finish the job and pretty much burned up a full tank of air.
I now pleasure boat and do not carry any diving gear aboard other than mask and flippers. I would not consider going under my vessel to remove a line unless I had no other choice. Rather just hire the job done, if possible.
But, please, do not even consider diving with compressed air without taking a basic course. Even, diving in shallow water can be extremely dangerous without the basic knowledge!