Excalion are not a particularly original band. Another review here likens their sound to leading power metal exponents such as Stratovarius and Sonata Arctica, and those comparisons are both quite fair to make - although I hear much more of the former and much less of the latter on this particular album.
That said, for what they do on this album, the Finnish band do it exceedingly well. There's nothing particularly original here - soaring vocals by a man whose trousers sometimes seem to be just a bit on the tight side, guitars and keyboards duelling away merrily to see which one will become the lead instrument, and a liberal helping of melody all over the place. The genre template is firmly in place, and just like seeing a James Bond film or listening to an Amon Amarth album, the listener will know precisely what to expect long before the first notes are played. Just like a good James Bond movie, as well, Excalion's work doesn't disappoint. Precisely by not being adventurous, the band has recorded a solid slab of power metal which is thoroughly enjoyable listening.
There are standout moments on most tracks here, however I'd suggest that the chorus of "I Failed You" is one of the more striking efforts overall. Emerging from a relatively bland track which seems incapable of becoming the power ballad it desperately wants to be, the first line ("I promised to keep you safe for eternity") is almost guaranteed to be a good punch between the eyes.
Keep your ears peeled for the bonus track at the end, too. This is a Finnish-language version of "Arriving as the Dark" which, despite the difficulties of singing in a language like Finnish, is still just as catchy and melodic as the English version.
In conclusion, this is a like-it-or-loathe-it proposition. If you can tell Timo Tolkki from Tony Kakko and (perhaps more importantly) listen to both without feeling ill, "Waterlines" will be a worthy inclusion in your collection. If the very concept of power metal is something you wish had never been invented, then keep looking elsewhere.