If you're talking about Dragon Slayer, you can't buy any boat.
You have to repair Ned's boat with a few planks and nails.
If you're talking about something else, well I'm sorry but the boats are not for sale.
i am not sure if you can make it but you can definitely buy it from port sarim.
You can buy one at Port Sarim Fishing Shop.
At a fishing shop in port sarim but chances are they will be out of stock, or off players or at the Grand Exchange.
Buy one at the port sarim magic shop for around 40gp each, or the grand exchange for 43gp.
you can buy eye of newts from the mage shop for 3gp in port sarim and sell them in the grand exchange for around 70gp :)
You should be able to buy on from the fishing shop in Port Sarim, you probably wont need it - but bring around 50gp just in case.
You cannot buy the blurite sword, you must smith the sword during a quest called "the knight's sword". At the end you get to keep it.
Check the Grand Exchange in northwest Varrock, you can find most items there. Also you can buy a ring mould in Rimmington, which is south of Falador and West of Port Sarim.
in karamja island (there is no bank there)
You can't. You can only repair the boat that is already there that Ned told you about.
yes if u mean a grocery store where u could buy food or something like that you should go to port sarim its near lumbridge when you arrive there you check the map and find the food shop near the fish shop and there you go hope this helps
First you have to buy fishing bait from either the grand exchange or the shop in lumbridge or port sarim. you then keep the bait and pole in you backpack and go fish. (hint) if you keep 27 fishing bait in your pack you can catch an extra fish per trip.