Ask Mr. Smarty Plants

There are many small native trees in your area. However your combined list of requirements: full sun, possible salt air and having it be showy enough for a focal point for your bench, narrows it down to fewer options. 

Ilex vomiter (Yaupon) is probably your best choice for exactly what you are looking for. Yaupon is a smaller tree not reaching a height over 25'. It is evergreen, which is nice, in terms of creating a shade canopy that you can enjoy all year long. It also can be shaped and pruned to your hearts content. 

There are many varieties commercially available now, some are dwarf, some are weeping. They all will have bright red berries in the winter if you are careful to make sure you buy both male and female trees. Your local nursery should be able to help you out with that.

A second option would be a Cercis canadensis (Eastern redbud). Redbud is a darling tree when it is in bloom. As it is deciduous, you will have to decide if it is worth not having leaves in the winter for the spectacular blooms in the spring. The other issue is the wind you mention. The trees would be fine. The blooms however are light and papery so they may blow off faster than they normally would in the conditions you mention.

Lastly Cornus florida (Flowering dogwood) might also me a great option. If you read about the dogwood you will see that is it listed as a partial shade tree. However dogwood is a tough-as-nails tree, and can handle sun. Occasionally the tips of the leaves might turn a bit brown with sunburn but over all the tree should do well. Dogwood is a classical flowering tree for your bench. The branches of the dogwood grow almost horizontally so you can prune this one to be a rooftop canopy over your bench. It also would be a good choice for handing the wind and the salty air.

So the choice is going to come down to what it is that you are envisioning as a look. Read all about he trees by clicking on the links and take a look at the photos provided in their records. These should give you some idea of what they trees will look like once matured.