Depending on the depth.
For shallow water (up to 10 meters) you will be fine with any model, if you go deeper, you’ll need an Ultra, as the regular one doesn’t have enough protection.
Plus - you won’t get any depth data from a regular watch as it lacks the corresponding hardware.
I used Groceries app for this purpose for a while. After iOS 17/WatchOS 10 I’ve switched to native Reminders and created a shopping list there. It has all the features I need and it syncs better between the phone and the watch (I had several instances when I went to the grocery store without a phone only to discover that the latest changes to my list in Groceries weren’t synced).