Blacktip Reef, National Aquarium

Blacktip Reef is a 265,000-gallon reconstruction of a shallow Indo-Pacific reef, dropped into the middle of Baltimore's Inner Harbor. Around 700 animals from some 65 species live in it, and this live camera looks straight into the tank.

Blacktip reef sharks patrol the upper water, rays work the sand, and hundreds of small tropical fish move over the coral in shifting clouds. Green sea turtles are the crowd-stoppers, cruising the length of the exhibit at their own unbothered pace; the aquarium has long taken in rescued turtles that could not be returned to the wild.

The aquarium runs on Eastern time, UTC−5. Feeding and diver sessions during opening hours stir everything up; late at night the tank settles into something much slower and, if you like reef cams for the calm, better.