BAT TAILS: just like in the ocean, bat tails are best for prone. not
much more to say. for the suggested nose width for prone, see cresent tails.

CRESENT TAILS: in the ocean, cresent tail board are usually best
for drop knee. on a flowrider, cresent tail boards are great for both
prone and drop knee.
there is an acception to this though. if the nose on a cresent tail
is too small, it won't work well with prone. if you plan to ride prone
alot with a cresent tail board, make sure the nose is between 10 and 12
inches. no more, no less. 11 is about perfect for prone.
if it's for drop knee, have the nose between 8 and 12 inches. 10 is about
perfect for drop knee.

WING TAILS: wing tails are between bat tails and cresent tails. you 
get the best of both worlds. works great with prone and drop knee.
it has a major drawback though. if your not an experienced rider,
you may have some trouble keeping the tail from catching in the water.
after using a wing tail for awile, it's not a problem anymore. it
doesn't take too long to adjust if your an experienced rider.
for the suggested nose widths for prone and drop knee, see cresent tails.

FLOW TAILS: made just for flowriders. great for both experienced and
amature riders. works great with any riding position.

ROCKER: if a board has no rocker, it's flat. if it has some rocker,
it's curved. most ocean boards are flat, and most flowboards have lots 
of rocker.
more rocker will give you better handling, and less rocker will give
you more speed. naturally, this means ocean boards are usually faster.

NOSE WIDTH: different from rocker, but does basically the same things for
handling and speed.
smaller noses give you more speed and wider noses give you better
handling.
don't use boards with noses wider than 12 inches. boards with wide noses
can easily catch in the water.

RAILS: the lower your rails are, the easier they can catch in the water,
but when the rails are lower, you get more speed.
50/50 is fastest, 60/40 is second, 70/30 is slowest. most flowboards use
70/30 railes. the 3 types of rails listed above are not the only rails, but
those are the standards for rails.