For the word "Spearfishing" how hard would it be? I don't know what tools to use to check how hard it would be and don't know how anyway...
Check the keywords by Keyword Tool - adwords. Google you can find what is search value for that keyword. You can analyze the key words from there.
look for tips in below post to find out how hard it would be. http://forums.digitalpoint.com/showthread.php?t=1932909 I just spent few minutes on google searching this keyword. first few results got high Pagerank and they are using keyword in title and description adequately. I would suggest you to try some niches around this keyword based on what you are selling or targetting.
just search in google and research the top 10 competitors' sites. see their backlinks and pr, domain age etc.
Its not hard. If other can rank why not you. Just optimize website for the keywords and do off page. I think there is lots of posts that will help you.
Keyword has searches , but not very hard competition, i think sticking on basic SEO, without paid links or link exchange this keyword can be get-able in top 3.
my guess would be that if you could get a domain with Spearfishing in it and do a simple site with some basic on-page seo you could rank in the top 10, my worry would be trying to take number one spot of wikipedia.
hard or easy ... are relative .... to ammount of "effort" you willing to spend ........ but i believe you can do it ..... eventually