Welcome to the board!
There are two main choices that I am aware of - flush mount and bracket mount. The JL Audio series and Polks are very popular for round, flush mount installations. I've had two boats now which used Boston Acoustics Voyagers. These are bracket mount and sit just behind the rocket launchers under the hardtop. I don't play music especially loud these days but as a former sound engineer for a touring rock band, I have experienced LOUD beyond what most can imagine.
If you need to hear the music while on a wake board, you will need both amp power and speakers which will handle it. I'd recommend 4 speakers to distribute the power and lessen the strain. Bracket mount under the hardtop will allow more sound to be directed behind the boat. Check Internet stores for choices. Besides the BAs I have, Nile OS10s have a great rep. Good luck.