Hi Zipline,i'm going on my first whalewatch @ the end of the month in Kaikoura [NZ} can you offer advise please on cam settings i should be looking at,i have a canon 400D which i will have a 17-55mm f 2.8 attached,and a 40d 70-700 f 2.8 on that body.I normally shoot in AV,iso 100-400,centre point focus,cheers.
I'm sorry it's taken me so long to respond! I kept meaning to post, but then would forget again. 
I'm far from being an expert when it comes to photography and I'm still experimenting myself, but I've been shooting in AV mode with at 7.1 and ISO at 400. On bright sunny days I normally go -1 on exposure and on cloudy overcast days I normally go +1. I still get some shots that I'm not thrilled with, but at the same time I get some shots that I flip out over, so it's been hit or miss. It also depends on the sea conditions and how the captain turns the boat (into the glare, with the sun behind us, etc.). The lens I've been using for most of this season is the 55-250IS (IS off) and I've been very pleased with the shots I've taken home. Prior to this lens I used the 70-300mm.
One thing to watch out for is the spray. As I'm sure you're aware salt water is not a camera's friend. I usually keep my tucked into my sweater until we see the whales close enough to photograph. That way it doesn't get AS much moisture and spray. I still wipe it down when I get home just to be safe.
Best of luck! I'll look out for some shots on how you did. 
