Watch this! Record this! I can’t be more effusive about Blue Planet II, the latest entry in the astounding nature documentary series from the Planet Earth crew. Tonight is episode 2, “The Deep,” which utilizes the latest advances in technology, in both filmmaking and underwater exploration, to send its human filmmakers deeper in the ocean than any human has ever been before. They descend to a world of darkness where you’d expect nothing to be able to survive – and they find and photograph, instead, all manner of life. Luminescent creatures. Patient, predatory sharks. Cannabilistic killer squid (pictured). And other things, all of which will leave you amazed by nature, and by television.