Hi Matt, I like your gate design, well done! My two bobs worth, I was concerned that the main part of the gate only hangs from two points on the scrolls, it may pay to add a peg style hinge at the bottom corner to bear some of the weight.I assume that the upright off the wave forms a spring loaded catch, this may be better made from an old coil spring straightened out as mild steel may succumb to some over zealous person bending it too far and it not returning. Lastly, I'm not sure how far from the water you are up there, but protecting mild steel from salt spray may mean painting with a good quality paint. You could use stainless but that would induce pain in your wallet and hammering arm . Most of all have fun making it.
Cheers Ian
PS See you at Get Hammered