Hey there. The GTI is a good machine, but remember not to only dig the bell tones, or you will only get coins but no gold. It will work fine at the beach as long as you do not get the control box wet. There is a special setting for salt elimination. Press the "menu" button about 5 or 6 times until you see "salt elim" flashing, then press the "+" arrow button, the press the "operate" button - there you have it - you are good to go at the beach.
As others suggested you may also have to adjust the ground balance or sensitivity.
Hi Bob, and a great big "howdy" from Texas.
I've had my 1500 a couple years now and really like it. I've had only limited use of it on the beach but no problems. As stated above, keep the box dry. I use mine mainly in parks and play grounds. Love that bell tone but don't dig it alone. Best advice I could give you is: practice-practice-practice. Oh - and also have fun.
Sounds like you may have a dead speaker in the box...I mean if the volume only works with your headphones...try to reset batteries, then if that dont work, change your batteries and if that dont work...um... hot too sure Good luck...