The maximum water depth in our "Deep Blue" line of baths is up to 6" deeper than other baths with the same overall height. All typical baths have the overflow fitting located a few inches down from the top of the tub on the sidewall. The maximum water depth is only to the bottom edge of that overflow fitting, normally about 6" below the top edge of the tub.
Our "Deep Blue" models are designed with a special included overflow located in an alcove at the very top of the tub and is mounted horizontally. You can fill a deep blue model all the way to the top of the bathing well for the deepest soaking hot massage ever!