You've asked about one of my favourite haunts (as anyone who looks at my images will testify to - yawn). The thing I've found is - the coast has two or three big things going for it.
1. Colours. If you like shooting colour, the sunrise/sunset (pref) colours are great when they are reflected off wet rocks/the sea/ sand etc. Wide panoramas of sea and rugged coastline always make great landscapes. Wide angle lenses and a tripod essential, film to maximise the benefit of the colour like Velvia works well too. I find B&W works well for mood as well.
2. Nature. If you like shooting birdlife; then long focal-length, fast (F2.8) lenses with an additional 1.4 or 2x converter are helpful for more success. Else a stealthful approach, a bit of knowledge about bird habits and patience go a long way towards success.
3. Texture and form. This is the area that attracts me, and the coastline has plenty. The best way to exploit the T & F is to use fine grain B & W on large format gear. Takes more time to set up and as a consequence needs some forethought, but is very satisfying in the end result. I mainly use two focal lengths - 150 mm (= approx 50mm in 35mm format) and 90mm (= approx 28mm in 35mm format). Mainly use the 150 for isolating compositions I find interesting, and I think I'd use a longer focal length more if I had one. The difficult and changing extremes of lighting also make for a good challenge. If you don't have LF (yet) and want to try this type of image, use the finest grained film you can get.

So for me a lightweight 4x5 LF field camera, fine grain B&W film to capture the detail, texture & of sand and rocks. A couple of lenses, a good waterproof bag (got a story I could tell about that), and coffee if it's winter like here.

Re subjects, I find the sunsets and rises a bit unpredictable and overdone to keep my interest (but I keep some Velvia in the bag just in case). I like to find an area that seems to have potential for texture and form and Practice. Not adverse to going back to the same place several times and trying the same thing in a different way. You may find that could help with channeling the interest into a particular theme, until boredom really takes over and it's time to try something else. Have Fun .

Edit: oops, just noticed we're in the 35mm forum (sorry no assumptions intended).