You will need to provide more detail for some good suggestions. What exactly happens when you try to restart at the end of the day? How many beeps and the sequence? Does it crank and no start or no crank at all? Any other noises? Dash light up normally? Does it start fine the next day or next time when cold engine?
At first blush, something seems heat related to me and the starter and or solenoid may be suspect. Maybe contacts are not working when hot. But some experienced diagnostic work is likely needed to check for power at the starter after a long ride on the water.