I agree with Marie. I see indications that your site has been negatively impacted by Google Penguin 3.0.
Viewing your site on semrush, I see that your loss in traffic occurred in October '14 -- the same timeframe in which Penguin 3.0 was rolled out.
I also see only "money" keywords populating your website's link profile (e.g. "alaska yacht charters," "alaska charter boats," "alaskan yacht charters", etc.). In other words, these links appear to be links that were created by you (or by extension, an SEO company) for the purpose of increasing Google rankings. Google considers this to be a "link scheme" and penalizes this activity: https://support.google.com/webmasters/answer/66356?hl=en
To move forward, I would first make sure that your website is verified/connected to Google's Webmaster Tools (https://www.google.com/webmasters/tools/home?hl=en). It's 100% free and you can simply upload a verification file to your server to get started. From there, you can review your website's inbound links and anchor texts. I would do a lot of research on DIY link audits before considering doing one yourself, but I can tell you that Google recommends being ruthless. Don't just pick a link or two that come from a Russian site. You have to be objective and honest about the links pointing to your site and whether or not they were created for the sole purpose of improving your ranking for a keyword. https://www.seroundtable.com/google-disavow-machete-16844.html
The first step for removing links is to simply reach out to the webmaster of a site/directory containing a dubious backlink and kindly ask them to help you remove it. If you had an SEO company build these links for you, ask them if they can provide you access to the user profiles they created to make these links. Hopefully you can just log in and get rid of the link yourself.
Your success rate in removing links by email solicitation may be very low. Most won't respond. Some may even ask for money. Never do this(!!!). It isn't the end of the world if you can't remove a link. Google has provided us a disavow tool that you can use to simply write off these links instead. They won't count toward your SEO anymore, but they can't count against you either (in theory). https://support.google.com/webmasters/answer/2648487?hl=en
If you can clean up your backlinks, then you have a shot at recovery, but this can only happen once Penguin refreshes again. We have no idea when this will be. It took over one year(!) between Penguin 2.1 and Penguin 3.0.
For that reason, you may actually want to consider building a new site in the meantime. More info on whether you should do that or not here: https://www.seroundtable.com/google-penalty-new-site-18200.html