How to get to Dismal Island?

[Colonel Vance]

This is my first run in the game, so please avoid spoilers and excuse me for my little knowledge of the game.

So, I've just opened the path to Shardy's boat, so I can travel around. However, I also gave some TNT to the bad guys who blew up Bob's Dojo, so I can't buy the Dismal Map anymore.
I've overwritten my previous save (didn't intend to) so I can't even go back and just not give the guys the TNT. So... how can I go forward in the game? Should I do all over again?

[wcc]

You won't get to Dismal Island anymore, and you don't need to. Just take your nose out of walktroughs telling you about every facet of (optional) content, and go on with the game.

[Colonel Vance]

I've never used a walkthrough since when I've started the game. I just thought I needed to go there since I first found the map and then a guy asking me for a map.

Anyway, I've used an older save to actually get there before reading your comment, and I've seen it's useless. The problem is I don't actually know where to go... well, looks like I'll find a way somehow. Thanks anyway.