Swimming: why is breaststroke slower than front crawl?
Breaststroke speed versus front crawl speed: John Wood explains why swimming breaststroke is slower than swimming front crawl, due to its increased resistance
Swimming front crawl (well) is far quicker than breaststroke because you should be creating far less resistance, and you will have almost constant propulsion.
By comparison, breaststroke is swum with the hips and knees lower in the water, and because both arms and both legs move at the same time, there are dead spots every single stroke.
If you’re swimming in a wetsuit you will be slower still as the majority of wetsuits aren’t designed with lateral (sideways) mobility in mind; so pushing against the wetsuit may well cause additional, unnecessary fatigue.