We have been on 15 cruises have seen a total of seven whales, one small group of dolphins and flying fish on four occasions. There have been more fish on my dinner plate than there have been in the water. I think I have been cursed by Murphy's Fish Law, "there are always more fish swimming near the other ship!" Perhaps if we take an Alaska cruise, still in the future, we may be able to see more fish.
The whales and dolphins swim on the surface, fish on the other hand would be mostly below the surface. Continue hoping that your cruise ships never put you in a position to be below the surface with the fish. Passengers only get to see quantities of fish if the ship is sinking. That would be the ultimate cruise gripe.
The trick to spotting sea life seems to involve learning to stare vacantly at the ocean for long periods of time. Eventually something pops into view and you'll have achieved your quota of excitement for the day. Does not combine well with casinos, bingo, pools or brisk walks on the outer prom deck; works with a drink at hand and feet up. The more sea days the better. Cameras are pointless, binoculars more pointless. If someone shouts "whale!" do not move - it's either a false id (ie. a log), or it is on the other side of the ship and will have disappeared by the time you get there. Whales do want to come to you but - like cats - in their own sweet time.
The fish are swimming along. Minding their own business. Along we come in our big old ship. It overtakes the slowest one in the school. Bumps it in the butt. It yells some thing like"On no! Here they come again". Everyone slides into the shadows til we are gone.
Actually Ive been on a cruise some yrs back that actually hit a big fish. I was on the aft. deck on the Holiday some yrs back heading out of Cabo San Lucas when I felt a shudder in the lower aft by the prop. A huge gush of blood spread like a pond in the wake as we continued on. I was shocked and quickly figured we must of hit either a bunch of dolphins or a whale that got in the prop. It was gross and bugged me for awhile, the crew just shrugged it off giving me an explination the whale must of been ill because they usually dont do that. Go Figure?