Never ever allow a Bulldog to swim or be near a pool or water source when unattended. Even when with someone, keep a very close eye on him and keep him in your site always while around water. While CPR is a good option to use in drowning's, it still has low odds of survival in Bulldogs....and best to avoid getting into that situation in the first place!
Bulldogs don't swim and will die fast, in a matter of seconds. It's always a safe choice to use a life vest on your bulldog while your with him swimming or near a water source. His weight may prevent you from holding him up or rescue of him. A swimming life vest prevents that. If you have a pool, be sure it has a dog safe fence with self latching gates, just like you would have for a child.