The Collaborative International Dictionary of English v.0.48:

Lacustral \La*cus"tral\, Lacustrine \La*cus"trine\, a. [L. lacus
   lake: cf. F. lacustral, lacustre.]
   Found in, or pertaining to, lakes or ponds, or growing in
   them; as, lacustrine flowers.
   [1913 Webster]

   Lacustrine deposits (Geol.), the deposits which have been
      accumulated in fresh-water areas.

   Lacustrine dwellings. See Lake dwellings, under Lake.
      [1913 Webster]

WordNet (r) 3.0 (2006):

lacustrine
    adj 1: of or relating to or living near lakes