No way, jose!
If Google teaches us anything about effective PPC, it's that the landing page should be what the visitor is expecting. This also applies with generic searches.
Thus, if someone is interested in sightseeing, they are simply going to end disappointed/frustrated if they reach a pitch for a cruise along the Thames/wherever.
Sure, you can design a series of PPC ads and direct each of them to a tailor made landing page, but I'd question whether the ROI would be anything to get excited about.
Cruises are cruises are cruises, and your site should focus on this and not try to tease people into it with some less than obvious keyword phrase.
With all due respect, the idea of several landing pages is another example of someone (with insufficient knowledge and experience) coming up with a magic answer. There isn't one.
SEO is rooted in relevant content not some sideways slithering!
Duncan