The Kelp Charger is great in this mode, you can snipe the enemy from a distance, use the sprinkler to help gain/keep control of the zone (and counter inkstrikes), then pull out a Killer Whale when you fill the special meter to force the enemy away. I try to not spend too much time in the splatzone itself, if you get splattered it spreads enemy ink, so getting splattered in the splat zone can give your enemy the opening they need to grab the lead.
One time I set myself up on the enemy side platform in Urchin Underpass after seeing the enemy try to use ours, it was really effective. They didn't use their side platform at all, so I got a free sniper nest in the perfect position to shut down enemy approaches, though obviously they still tried to splat me. A lot of people were subject to tunnel vision, not realizing the map had multiple approaches to use/worry about.