"It's very easy to put a block on my own progress, I assure you," Carlisle returns, his eyes still on the water. "Blocks are good for- for holding onto when you're fairly certain the water will drag you under."

Which it hasn't yet, but it does push against his ankles, encouraging him to go further, closer to death. Though well aware Glacius is right there and ready to grab him should something go wrong, he can't help his uncertainty.