Garrett INFINIUM LS (Land and Sea):  This detector performs remarkably well in heavy salt conditions.  It can be used underwater to a depth of 60 metres as well as on land. 

• Circuit type: For automatic cancellation of salt/ground mineralization this uses Pulse Induction technology
• Audio Threshold, Adjustable: user adjusts to suit preference
• User-Adjustable Discrimination with Quick Iron Check
• User-Adjustable Frequency: adjust to reduce interference
• Automatic Ground Track with 3 settings:
  • Slow—Use over slowly changing ground mineralization.
  • Lock—Locks ground track setting; use for most ground conditions
    and offers maximum depth.
  • Fast—Use over extreme or quickly changing ground mineralization.
• Volume Control: on land headphones (included)
• Salt Elimination Aid: at beach eliminates interference of salt mineralization
• Hip Mount Battery Pack: eases detector weight to enable long searches
• Battery Life: Alkaline (included), 10-15 hours. Battery recharger for AC and
  automobile included. Rechargeable (included), 7-10 hours.

Search Modes:

• Motion All Metal with adjustable PI discrimination