The Santa Cruz Extreme AO Lab (SEAL) is a new visible-wavelength testbed designed to advance the state of the art in wavefront control for high contrast imaging on large, segmented, ground-based telescopes. SEAL provides multiple options for simulating atmospheric turbulence, including a custom spatial light modulator. A 37-segment deformable mirror simulates the W. M. Keck Observatory segmented primary mirror. The adaptive optics system consists of a woofer/tweeter DM system, and four wavefront sensor arms: 1) a high-speed Shack-Hartmann WFS, 2) a reflective pyramid WFS, 3) vector-Zernike mask, and 4) a Fast Atmospheric SCC Technique demonstration arm. Finally, a science arm preliminarily includes a classical Lyot-style coronagraph. SEAL's real time control system is based on the CACAO package, and is designed to support the efficient transfer of software between SEAL and the Keck II AO system. In this paper, we present an overview of the design and first light performance of SEAL.