I've got a feeling I'll get beat up over this response, but you're looking for a solution.
The Echo remote can only reach so far. So... if your pool is farther than the remote's range, you'll
need to look for other options. In case you have some older technology sitting in a drawer somewhere
you can make your Dot respond from the pool.
The range on the ones I have is up to five miles. I tried it from six blocks away and all was well.
My Dot didn't seem offended having older technology sitting by it and telling it what songs to play.
You can also use a landline phone if the base is near your Dot. Just take the remote outside and use the intercom feature if equipped.
I know, only an old guy would think of these solutions. Hey... It works.