It is important to figure out your child’s priorities. In reality, it is hard to focus on all 3 activities if your daughter attends a school with rigorous academics.
Since you listed academics at the top, I am going to assume that it is the most important consideration for your family. Academic strengths of each school are relatively easy to tell –– you can visit the school webpages and look into their curriculum, special programs, etc.
Now, in terms of strings, many top schools are capable of offering great teachers, private lessons, and even access to orchestras in nearby cities. Andover, Exeter and Milton, for example, have close ties with top institutions in the Boston area, such as NEC. Andover, in particular, has a Lawrence Strings program that you might want to look further into. Given its location, Choate also has good access to the strings teachers at Yale. Since they do not have Saturday classes, some of the musicians take trains into NYC and participate in Juilliard pre-college classes. For years, Hotchkiss is also known for recruiting and training conservatory-level violinists and cellists. All these schools are worth considering.
In terms of swim programs, I would look into Peddie and of course Lawrenceville and Andover (these two schools just built amazing new facilities in the last few years). Choate, Loomis, Exeter and Blair all have solid programs, as well.
When it comes to crew, @matadorski already gave you great advice. Many schools have rowing facilities right on campus or close to campus. For example, Choate sits right on a river, as do Kent and Milton. Blair, Peddie and Middlesex have a pond on campus, and Hotchkiss has a huge lake next to campus. At other schools, kids may have to have to travel 15-25 minutes to the closest boathouse.
Good luck with your school research.