Another fun fact! Since his aura of Mining Fatigue III is a debuff; you can kill the elder and immediately remove the debuff by drinking a bucket of milk! Be sure to have your second water breathing potion handy though!
I guess opinion perhaps; but if you obtain Depth Strider III, you will move in all directions besides up and down at 100% normal speed. This makes closing with the Guardians (between attacks, remember to interrupt that beam with any sight-blocking object!) quite easy. As a bonus; if normal speed still isn't fast enough, Depth Strider III allows you to further increase your movement speed with Swiftness potions! Truly alchemy is the bane of these creatures.