jIH:

> ej bIQ'a' HeHDaq maHtaHvIS, 

> majatlhchugh < DaH mamej >, vaj bIQ'a'

> HeHDaq qaS "the leaving"; 'ach origin 

> 'oHbe' bIQ'a' HeH'e'..

If while we're at the shore we say {DaH mamej}, then the "leaving" takes place at the shore, but the origin (that which is left behind) isn't the shore. 

The "leaving" takes place at the shore, but the shore isn't left behing. We're moving along the shore, from one point to another.

If you're walking along the shore, you're not leaving the shore, so you wouldn't say bIQ'a' HeH wImej. If you say mamej, then you're leaving someplace, but you're not being specific about which place you're leaving (because it's obvious). If you wanted to be very specific, you could say Daqvam wImej or whatever, but you have to actually leave the place you say you're leaving for it to be correct.

I still don't see your problem.

-- 
SuStel
http://trimboli.name