Hey, If you have the MAP PACK, the insert/cover folder thingy, lists for Water:
WATER (DEPTH 0)
Line of sight (LOS): No effect
MP Modifier: None
PSR Modifier: None
Attack Target Number Modifer: None
Compare to:
WATER (DEPTH 1)
Line of sight (LOS): No effect
MP Modifier: +1; level change costs are not included. See Movement in Water, p. 19 BM, or Underwater Movement, p. 56, TW
PSR Modifier: -1
Attack Target Number Modifier: None, but it provides partial cover to 'Mech standing within it (see Partial Cover, p. 26 BM, or p. 102, TW).
In other words, the cover-flap has ALL the Hex types coverd for you ;) All the Buildings, the CLEAR, Pavement, Rough, Water, and Woods terrain.