Live in the area the last 20 years. Never done the boat ride. As far as the best places to view the fireworks:
1)The Mall between the Capital and the Washington Monument.
2)Along side the reflecting pool between the WWII Memorial and the Lincoln Memorial.
3)The Eclipse behind the White House.
I believe all three places you will clearly see the fireworks up close and hear accompaniment by The National Symphony Orchestra.
Metro is the only way to travel. Don't even think about driving. This event draws around 700,000 people It will be very very very crowded. Oh did i mention it would be crowded? Get there early and hang around after the show for a good while. Metro will be packed beyond belief at least 90 mins after the show.
But its a great show, only second to NYC. Well worth seeing at least once.