I created a water entity, so I checked the case "Is water entity", and I added everything to make a Water Entity, but when I spawn my entity in the water, it dies after few seconds.
I took screenshots of the settings of the Water Entity. https://imgur.com/a/zB7rFlQ
You can see here that crabs drown into the water. https://i.imgur.com/Xt7VRTL.mp4