Find a video and sounds
Checkout videoblocks. They are a subscription based stock footage site.
Here is a clip I found that is similar to what you are looking for.
Consider using my referal link to sign up for videoblocks.



For sound effects, check out audioblocks (a sister sight to videoblocks).
They have sound effects for dolphins, whales, and lots of different water sounds.
Consider using my referral link to sign up for audioblocks. 

P.S. I am not affiliated with videoblocks or audioblocks in any way.