Giuseppe,
Aloha! I live a litte over a mile from the tropical Pacific, and my brass rails are holding up fine! i am told my plastic ties may suffer in time, but, after 5 years in the sun, they seem to be OK. I also have really sandy soil. We used a raised bed and had the fill packed. It did settle, but it got us over the hump!
I blogged our efforts here in thread entitled "Progress on the Triple O." Given our similar climate and location relative to the sea, you may find thins of value there. Also, forum member Bill B., who posts as Chochowilly, lives in your neck of the woods. I have been mining him for data for years since he reached out to me!
In the words of the late, great Tom Trigg, "Get outside and get dirty!"
Eric