Sorry for your loss, John. I lost an avocado tree last year. No visible flood, but the tree was planted in the ground and the rain coming off the roof probably caused the ground to become saturated. Another avocado planted in the same spot but in a raised bed is thriving. Even if you manage to nurse your tree back to health, you will could face the same problem next time we get heavy rains in Pinellas. May be better to dig it out, created a raised bed and planted a grafted variety.
Mark in Texas, your avo looks good! How old was the tree when the picture was taken?