Another pair of homonyms with similar/identical meaning. A dictionary check gives me this:
濱 (1) 水邊。如：「河濱」、「海濱」、「她喜歡在湖濱散步。」 (2) 靠近。如：「濱臨」、「濱海公路」。
瀕 (1) 水邊。如：「河瀕」、「江瀕」。 (2) 臨近、迫近。如：「瀕臨」、「瀕危」。
This isn't very helpful since the definitions of the two characters are almost identical (including some of the examples). However, I do think that 瀕 is more often used in sense (2): 瀕臨，瀕危，瀕於 and so on, and that 濱 is more used in sense (1): 濱海，濱河，濱江. Some quick google checks seem confirms this.
Hypothesis: From a practical, modern point of view, they mean the same thing, but there is a preference for 濱 in the sense of being close to water and 瀕 in the more general sense of being close to something (even something more abstract).
Is this correct? Can these characters be used interchangeably, even if there seems to be a preference for one over the other in certain situations?