When you consider that Noah's Ark is a biblical, old-testament story from Genesis, which is historically dubious if you look at it objectively--it didn't happen--I doubt this is the right subreddit for this. /r/Christianity or /r/theology might serve you better.

assuming the story is true, there would really be no reason for Noah to gather acquatic animals. They would not be affected by any such flood. He probably had enuf to do just finding food for all the elephants, zebras, giraffes etc. just imagine the storage problem.