Go to Misty Mire in Tortuga, and attack the giant crabs, big alligators, and huge alligators using only grenades. They will not attack back.
Easy Kills
If you need help getting your level up then go to port royal, then go to Fort Charles and go to the hanging station. There should be a grunt from level 14- 18 attack him and we won't attack back! But dont go off the platfrom or he will start to attack you and get veterans to help him! Happy Plundering.
Easy sailing and cannon rep
To level on sailing and cannon fast join a crew and plunder high lvl ships and board EITC ships. Doing this will also give you alot of gold, plus if your the captin you'll gain more xp and gold from your plunders.