Flush Mount Speakers Can be installed in tight spaces and out of the way of most activity. However, you also have to cut a hole in your boat to get them in place. Cutting a hole in your boat might seem counterintuitive, but it really isn't as bad as it sounds. It does take effort and planning, though.
Flush mount speakers require relatively enclosed air space around the back of the speaker when they are mounted in order to get the best resonance and frequency response. If the back of the speaker is exposed to open air it can sound tinny and weak without a lot of bass. We do carry speaker enclosures that might work in certain installation situations.
Box Speakers Don't require you to cut a hole in your boat and the box enclosure is already set for optimum performance of the speaker so you don't have to worry about the air space around it. Gimbal brackets make them easy to mount and easy to aim so that you can put them in position for optimal sound quality.
The main disadvantage is that they can take up space on your boat that flush mount speakers don't. Which can be a real pain, especially on smaller boats.
Wakeboard tower speakers like this are larger box speakers that come with a clamp for mounting to the bar of a wakeboard tower. As you can see, many of these are large and powerful and capable of producing night club quality sound that skiers and wakeboarders can hear over the sound of the engine and the waves.
Smaller box speakers can also be mounted to a bar like a bimini top using P - clamps which are available in the conduit section of your local home improvement store.