As underwater still photography benefits from strobes, underwater video is better with video lights. Water strips warm colors from sunlight as you dive deeper. Artificial lights sources (video lights) help to add the warm colors back into your shots during daylight, and they provide a primary source of light during night dives.
If you’re new to underwater video and only dive in open water during daylight, consider just adding video lights down the road. Most of today’s camcorders have relatively decent low-light sensitivity so you may be content with the results you get without video lights. One you gain experience you’ll have a better idea if you’ll benefit from video lights.
Most housing manufacturers sell video lightning kits that are designed to integrate well with their housings. These kits include light heads, arms, cables, switch assemblies, and battery packs. Several flavors of lightning technologies are available. Halogen is the most reliable and inexpensive. HID (high-intensity discharge) systems provide a whiter light and longer burn times per battery charge with the trade-off of being less reliable and more expensive to maintain.