I believe that baptisms can be held in any body of water, so a jacuzzi would do fine. What matters is that a person is surrounded by other believers and they are making the choice to be baptized for Christ. 

It's about the heart and not formalities. Jesus never specifically talked about how we should do it. Just that it would be done. He told us not to use a jacuzzi or even to use a jacuzzi. 

Therefore, go and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit. [Mat 28:19 NLT]
Teach these new disciples to obey all the commands I have given you. And be sure of this: I am with you always, even to the end of the age." [Mat 28:20 NLT]