So you don't get discouraged at inevitable setbacks, read Farley Mowat's THE BOAT THAT WOULDN'T FLOAT and Jack London's CRUISE OF THE SNARK.

The inevitable GUN has been mentioned. My personal favourite boatgun is a SMLE. The things hold 10 rounds, are capable of VERY rapid controlled fire, are near impervious to climate and have sloppy chambers that digest the worst of ammo ( But buy a nice supply of fresh rounds, and if possible load up a box of aussie RINO 215 grainers.) You can still find them relatively cheap, and if one has been Frankensteined into a sporter even less. get one of the later versions with peep sights.

If you cannot afford, or do not want firearms, buy a box of big nails and scrap lumber and make pungy boards. A famous solo sailor was surrounded by hostile natives in the 19th century. He merely scattered TACKS on the deck and went below for tea.

DO NOT change your boat's name. It's bad luck.