The Sea Hunter is a "PI" and it's strengths are depth. Like all PI's, it will beep on everything and will do so at scary depths. It is also capable of running smoothly in the most highly mineralized soils and salt water. For water hunting, it gets the gold rings and coins that others didn't because they were too deep or they machines used could barely cope with the salt water and or mineralization.
The Sea hunter is a dig all machine, and is not the choice for parks and trashy areas. However, it will run circles around most other detectors in the water, especially futher away from the shore line where there is less trash.
The AT Pro has a unique ability using audio and VDI numbers to ID with a good probability, allowing the user to leave a lot of the junk in the ground.
I had a Sea hunter, sold it and replaced it with another Garrett PI, the "Infinium" which even squeeze a little more depth then the Sea hunter. Of course the "AT", Sea Hunter & Infinium are all water proof, and when used properly in the right location, are killers for good finds. Unless you never will water hunt, keep the Sea Hunter. Getting an AT Pro or AT Gold and still keeping the Sea Hunter gives you a great detecting arsenal. Most serious detectorists have more then one machine. I presently own about 12 detectors.