I was going to go to the Cianwood City Gym, but then I remembered that Eusine was on the island as well, so I healed my Pokemon and then I headed north. I found the place where Suicune was resting, and I approached it. It ran away when I got too close, but then Eusine came to challenge me to a battle. We fought and it was a relatively normal battle. I beat Eusine and then after chatting a bit, he left. I returned to the Gym and I battled the first two Gym trainers within the Gym. I then had to make my way around to the other side to push the button that would stop the waterfall from falling on Chuck's head. I got that done after battling some more Gym trainers, and I saved before challening Chuck.