how about a seat in the middle facing out sea obviously with a raised railway sleeper planter each side up to seat 2 feet tall and 4 x 4 metres square and a smaller one behind the seat say 2 x 2 metres leaving the same in front for your seat build a pagoda or arch type structure over the seat and put trellis up the back and sides and grow some hardy climbers up the back and sides to keep the wind of and you hidden . id say a water feacture but I guess you got a great one lol . then plant each side up . obviously you could use different materials etc . its just a thaught , a few photos would be inspiring .

Any chance of some photos of the area? And which way does it face (east, west, whatever) and does it get sun or is it shady, or shaded by something?

If you Google Seaside Plants you'll find lots of ideas for plants that will be happy in that situation, that might inspire you with some ideas.