JW Marriott Hotel Shanghai at Tomorrow Square | 酒店上海明天广场JW万豪明天广场

One of the lanes is a regular width, the other is really wide.

The 25m pool at the JW Marriott Shanghai opens at 6am, has two lanes, is well maintained, very clean, and the right temperature for knocking out lengths. The changing rooms are excellent with plush towels, free slippers, complementary shampoo, conditioner, shaving, and teeth cleaning kits. The only problem is you have to find the pool. It's on the fourth floor and hidden down a maze of corridors.