Ha ha yeah all the best with that!

What my midwife said was that home spas are good (cos you have control over them, and are aware/used to the bacteria there).
With the temperature, if you get too hot, well, get out!
And with public spas, there is more bacteria around. For example, she said a girl who works at a public pool would be fine because her body's used to all the bacteria, but maybe other people would be more cautious.

I reckon your butt would have to be pretty close to a jet to get air up there, cos of your plug and all, but really, check with your dr/midwife if it does turn out you're preggers and ask them 'why' so you understand their rationale behind why something is safe and not safe. Like, if your dr says totally safe (because problems are just rare) that is different to totally safe (because physically it can't be an issue). If that makes sense..

Anyway, I will conclude this ramble by saying All the best, and have fun!