2009 challenger180 died won't start please help a rookie

[300wsm]

Hi, so I recently purchased a 2009 challenger and may have taken on too much water As the engine died I got towed into shore said 12 volt was low on dash so I charged battery everything looked fine so off to the water I went to see ....boat started but low rpm didn't want to move than it died did that twice than just wouldn't start ... Where do I start now lol thanks