This looks like a sculpted carved cake but I was wondering how many cakes and what sizes to use for it to give it the wavy sea look.

Also, how would you do the whale... the lady also wants a shark on one side and the whale on the other.... TIA!

Edited: Found the bigger version!

My guess is the actual cakes are 8 or 9"x4 and 6x4 and the dolphin is fondant OR carved from a small sq.
Of course I could be totally wrong but that's what it looks like to me.

Thanks kakeladi! Do you think it will look good if I just use a flat cut-out of the whale and do the tail jutting out like the pic with gumpaste?

Will it look seamless with the flat whale and 3D tail?

It is a little hard to tell but I think I'd try that. Maybe you could do a small test version.......just make the whale (flat) and put it against some dummy tiers OR pans about the size you want to use. (drape the pans/dummy w.some fabric or such for the test.)
As for trying to make the tail seamless.....put it behind the body and smooth some fondant over/into the tail part.