Jinbei admitted that he’s of no use on land battles, implying he’s much stronger at sea.
It’s said that Jinbe was able to fight Portgas D. Ace on similar terms, despite Ace holding Logia Devil Fruit powers. They both almost killed each other in a five-day long battle, just before Ace was taken in by Whitebeard and in Prison Impel Down, he and Ace shared a cell on Level six. He was able to effortlessly punch Gekko Moriah a few meters away, almost knocking him out.
He can move and manipulate huge amounts of water and launch it so fast that it destroys battleships. And remember when he damaged Luffy by forming a shockwave with the water in the air?
Guess what that attack is like in the ocean.
Even for a Fishman, Jinbe holds tremendous strength. He’s the most strongest Fishman seen so far, shown when he threw away a giant Fishman with just one kick.
He knocked out Charlotte Opera, an enormous man more significant than himself in one punch.
He also used Buraikan to send the Big Mom off the Thousand Sunny with enormous force. This was an extraordinary feat as Jinbe was the first person seen to knock her down.
Due to his enormous mastery of Fishman Karate supplemented with his physical prowess, Jinbe can do big defensive blocks to stop attacks as powerful as the attacks from a shadow-strengthened Gekko Moriah.
Jinbe easily defeated Caribou, a Logia Devil Fruit user, with a Haki, enhanced punch. He can harden his fists. As revealed, when he defended himself against some Big Mom Pirates. He could strengthen his arms and protect himself against Big Mom’s Cognac.
Jinbe is a mighty master of Fishman Karate, which he can use to knock away many opponents at once and defeat powerful enemies. He was a child prodigy, being skillful enough that he became a black belt, while he was still a child. By adulthood, Jinbe’s ability in Fishman Karate has become so enormous that his strikes didn’t need to make physical touch with an opponent. As the water particles in the atmosphere will blow them off, after a few seconds of time from the attack’s initiation.
As a Fishman who is very close to the sea, Jinbe is a dominating helmsman, as revealed when he steered a stolen Marine battleship from Impel Down. He succeeded to skillfully drive the Thousand Sunny on his first try and also rode the ship within the ‘Green Room’ of the huge wave homie Big Mom created, using his Tacking abilities. Nami said about Jinbe’s skills as a helmsman as if he were managing the ship like his own body.
In my opinion, Jimbei is insanely strong. While Luffy, Zoro, and most reasonably Sanji might be somewhat above him on land, he’d most likely crush them in the water.