You could use beachy themed papers and embellishments to create traditional embellishments...Christmas tree from 'water' colored paper with a starfish topper..stockings hung on a beach fence and made from beachy colors...

Here's some paper I found in the sb.com store

SugarTree - 12 x 12 Paper - Sandy Claus

You could easily use this piece of paper to do a 2 page spread. Tear it donw the middle between the tree and santa and put the tree on the left edge of one page and maybe trim the santa side a little closer to the santa and adhere it to the right edge of your 2nd page.