I can personally & highly recommend a set of custom waterproof headphones from Tony Eisenhower. Tony's standard set have thinner white cups. But for me, I wanted the quietest and loudest headphones I could get, so I could hear whisper signals & threshold nulls over all the screaming, tow planes flying overhead, diesel go-fast boats whizzing by the coast, etc. So, Tony made me a set of his diver's headphones using his larger blue cups. All his headphones are waterproof, the only difference with his diver's version is that he drills a couple holes at the bottom of each cup, to allow water to empty faster. I always wash all my gear with fresh water after every hunt, so the holes allow the water to drain from the cups faster. When hunting, I put electrical tape over the holes to help keep wind noise out.
Tony's larger blue cups provide more noise attenuation, i.e., are quieter. He also added his impedance matching circuitry which provides louder volume, which was exactly what I was looking for, quieter phones AND louder tones. His phones are extremely comfortable as his headband splits into 2 sections, which spreads the band out on top of the head. They fit tightly over the ears, and I purposely tried shaking my head to see if they would fall off, but they stuck to my ears like glue. I've worn them for hours hunting on the beach and forgot they were on my head. He makes his phones for a variety of detectors, including Minelab X-Terra Elite, NOX's, CTX303, etc. Although I also have an X-Terra Elite, these blue cup phones were for my Dual Field PI, which was modded by OBN to use a Minelab CTX3030 waterproof connector, so he used that connector and my phones connect perfectly.
BTW, the insane thing is that you can get a set of his custom waterproof headphones for about $10 more than what the stock, crappy Minelab waterproof headphones cost, so getting his phones is a no brainer. Tony doesn't have a website, so you'd need to contact him via email. AND, if you put something like "Tony, Sand Hunter on the Friendly Forum referred you" in the emails subject line, he'll see that and just might give you priority. Just saying, lol.

Here's his email:
[email protected].