I have a similar problem, and have lot of trouble with my ears, especially flying, and have even had to pull over for a few minutes when driving down a long hill. I fight my tubes constantly (even sitting here in the office).
I do dive, and have had to abort a couple of dives because I couldnt get my ears to clear. However, I have had a lot of successful dives. I have found that if I take Sudafed before the dive and do slow descents I can dive without problems. I use the long-acting Sudafed (12- or 24-hour) to make sure that it wont wear off during the dive. The Divers Alert Network says Sudafed and nasal sprays are OK with the approval of your doctor.
If you cant clear you ears while snorkeling (free diving), dont let that influence your decision on whether to SCUBA. When you dive with SCUBA gear, your descents and ascents can be much slower, so the pressure change is slower, and SCUBA allows you much more time to equalize your ears.
Im not qualified to say that your ENT is wrong, just that you should get a second opinion. Especially if your current ENT is not a diver or specifically knowledgeable about dive medicine.
Also, do some reading (on this board and otherwise) on the different ear-clearing methods, and make sure you get a mask that gives you good access to hold your nose, even with the regulator in your mouth.
Good luck.