Clip this device onto your bcd so it's handy when you need to get your diving buddy's attention. A magnet is located inside on either end of the shaker with a ball bearing in between. Shaking the device moves the ball bearing, creating a loud Echo sound underwater. It's a great communication system when in a world where words simply won't be heard..

A useful underwater safety device. Great for underwater communication. Shaking the device moves the ball bearing, creating a loud echo sound underwater. Magnet is located inside on either end of the shaker with a ball bearing in between. Uses a special magnetic system.

Date First Available: November 5, 2011. Best Sellers Rank: #65,881 in Sports & Outdoors. Customer Reviews: 4.5 out of 5 stars 336 ratings 4.5 out of 5 stars. : B002ZDP7PI. Size: ?Medium. Included Components: ?Mares Magnetic Shaker Scuba Diving Communication Device. Model Year: ?2016. Part Number: ?415172. Manufacturer: ?Mares. Color: ?Black. Brand Name: ?Mares. Item Weight: ?0.1 Kilograms. Item Dimensions LxWxH: ?7 x 1 x 1 inches. Package Weight: ?0.12 Kilograms. Item Package Dimensions L x W x H: ?10.5 x 5.6 x 0.6 inches.