I really like this! Precisely seventeen syllables:)
I love the description you've used for them. I also enjoyed how you've centered it, as I thing presentation is a big part in a poem ( personally ) But a top tip for haikus/ senryus/sytuits: they're only three lines long, but the title doesn't count. Use the title as a sneaky fourth line ( it's cheating, but everyone does it! ) and maybe play around with it a bit. Puns and things like that are always clever. Still, I see the point in keeping it as just whale, as you're not mentioning the word whale in the actual verse. Things like that.
Anyway, I thought this was lovely!

i love whales, especially when they surface and breathe a fountain of sea water out of their blowholes. Thanks for sharing images of this wonderful mammal.

Perhaps, you could try another, incorporating the image i have just described?