Wailord isn't obtainable until after you defeat Norman. It has low defenses and speed, and its attack stats are only slightly above average. It can learn earthquake, but earthquake won't get STAB and is super effective against very few late-game opponents.
Pelipper and Tentacruel are both pretty useful. Wingull learns water gun and wing attack while Tentacool is stuck with cut and acid, but Tentacool learns bubblebeam. Tentacruel has higher physical attack and speed, which makes it better at a mixed attacker (with surf, sludge bomb, and ice beam) in the late game.
If you're okay with using other Pokemon, Sharpedo and Starmie might be better. Sharpedo's special attack isn't the best, but it has high speed and gets STAB when using crunch. Starmie has high special attack and speed and learns thunderbolt. Both crunch and thunderbolt are useful in many late-game boss battles.