One type of hand dredge I have used is my hands.  I collect handfuls of
sand from what looks to be good shell sand and put them into a ziplock
bag in my goody bag.  Collect from a variety of spots, including under
rubble.  I found a very large number of micro shells this way. And the
"dredge" take up little room in traveling or diving.  The same hand
samples are quite effective on the beach as well.  Find places where the
ratio of shells to other material is high and concentrate most time
there.
--
                     Aloha from Wesley M. Thorsson
Editor of Internet Hawaiian Shell News, a monthly Internet Publication
           122 Waialeale St, Honolulu, HI  96825-2020,  U.S.A
       http://www.hits.net/~hsn                 [log in to unmask]