Hoover Dam policy recommends that people with implanted ICDs do not tour the dam because of its 60Hz magnetic field. The magnetic environment within other hydroelectric plants, however, may differ so check with them to see what their policies are for people with ICDs. Being around such strong magnetic fields may result in your ICD delivering an inappropriate shock. Tour a non-hydroelectric dam if you want to see how great quantities of water are held back through the marvels of human engineering.