I am new to scripting but I managed to make this script which I think is pretty good. It took a while but here it is.
What it does:
Takes the ship between Karamja and Port Sarim, fishes lobsters, and banks them in the bank deposit box at sarim.
How to use:
1. Have more than 60 coins in your inventory for the boat. If you have below 60 the script will log out.
2. Have a lobster cage in your inventory.
3. Start the script anywhere around Karamja/Port Sarim and you should be good to go.
Have not had any problems with the script after running for 4 hours with breaks. Post here if you find something. Thanks!
Link to script download.
Edit: May have trouble if you have completed pirate's treasure. Not sure.