This was growing on the beach and has thick, succulent leaves.

My first thought was maybe a variety of Cakile lanceolata, commonly called "Sea Rocket" or Coastal Sea Rocket":

http://www.google.com/search?q...

I think you may be right. I photographed this unidentified one early this year, but they look so different, I never made the connection.

Cakile edentula looks closer, can't be sure it's correct ..

http://www.google.co.uk/search...

Cakile maritima might be a better match, look at locations.

http://fr.wikipedia.org/wiki/F...

http://plants.usda.gov/java/pr...

http://plants.usda.gov/java/pr...

I agree with Cakile maritima for this one. Additional information other than flowers, leaves and habitat - see the notation in the link below about "tinted with purple or magenta". The buds in Jay's picture are colored this way...

http://www.eattheweeds.com/the...