Rescue Delays

[Rongway]

That's because Rescue doesn't nullify knockback. It will pull them after the knockback has finished. Since the knockback slides them into the water, they're dead when they get pulled.

If you want to save someone from sliding off, you have to pull them before the knockback registers. I'm not 100% on whether knockback cancels a rescue pull. If it does and they're only halfway to safety, it might still kill them. If not, it would either give you some wonky motion effects as the player teleports to you faster than they should, then gets pushed, or the knockback would just appear to knock them back less distance than everyone else.

Knockbacks, teleports, gap closers, disengagers, and pulls all override each other. It's just a matter of timing. You can Rescue someone as they're about to get knocked back as long as the knockback hits them before Rescue does. The timing is just unnecessarily complicated by the inconsistent activation time of Rescue and other "instant" movement abilities.