Im not 100% on all my furniture in the game but I would be looking at doing something like.. on one of the side rooms make it look like a beach, put up a deck chair and an umbrella and something water like to splash in, put a sandy or water like pattern on the floor and a sky wallpaper up. Then for the rest of the house do it in furniture styles that look semi rustic but bleached/white in color. A lot of places when they do beach or nautical themes will use Blue stripes as a main theme. But you can also go with the blue white and one red stripe. find anything that looks like rope, cane, lighthouses, seagulls, shells, etc. If there isn't any water theme, then look for something with a blue swirl to it.
If I get some time I will look up some furniture for you
At a quick glance you could go with the alpine set and just put in a blue and white stripe effect pattern into it.
The ranch set can be turned into a white set and it looks kind of rustic. Minimalist set in white could be used if you wanted something a little more sleek. The stripe set can have blue stripes in it so you could definitely use that. just add some red accents around the room.
look for Urns, anchors, bottled ships, boxing mats (as make shift towels), Carp banner, Coconut palm, Fish set items, hula dolls, hibiscus clock, mermaid statue... there are some things off the top of my head for accent items.
