Here are some of the best coastal tabletop decor ideas to inspire your own!
Great mix of colors and elements make this coastal table a fun feast for the eye, using Pottery Barn Tableware. For tips on this coastal tabletop decor, read the posting on Pottery Barn's Blog.

Sandy colors anchor this Blue Coastal Table Setting by In My Own Style. The simple Wooden Candle Lantern is filled with sand and tiny shells.
Eclectic

Shellicious
Neutral seashell theme tabletop decor idea that includes Shell Dinnerware, Shell Charger Plates and a lovely Hydrangea Flower Arrangement with Shells. All set on a large Burlap Tablecloth. Via Home Is Where The Boat Is.Flower Power
A large bouquet of hydrangeas, some live others faux, sit in the center of this coastal table setting that uses a Table Runner and some nifty DIY Coastal Napkin Rings made with cut up toilet paper rolls. Via Calypso in the Country
Create an instant Nautical Tablescape with a Decorative Fishnet. Drape a decorative fishnet along the center of your table as seen in this picture, or over the entire table as other pictures will show when you follow the link. The Blue Coastal Dinnerware chosen gives this table a bright and breeze beach vibe. Idea by Life Family Fun.
Set your table with an unexpected Tiered Tray Centerpiece, filled with shells or other coastal theme items such as Seaglass, Driftwood Pieces, and Fishing Glass Floats.
This contrast rich coastal beach tabletop decor idea exudes a summer vibe. A bright blue tablecloth sets the tone and orange just pops so beautifully. And the DIY Shell Napkin is perfect -click the link to see more ideas like this.
Bring your idea of a tropical paradise to your table with Tropical Palm & Leaf Decor.

Throw a Net

Tray Chic Centerpiece
Set your table with an unexpected Tiered Tray Centerpiece, filled with shells or other coastal theme items such as Seaglass, Driftwood Pieces, and Fishing Glass Floats.

Sunny Orange

Tropical Paradise