Sea&Sea Announces Housing for Sony Alpha Series

Sea&Sea has announced a universal housing for Sony Alpha series cameras. The MDX-au is currently compatible with the a7 Mark IV, a7R Mark IV, a7S Mark III, a9 Mark II, and a1, although there are modifications and limitations with some models (see below). The housing utilizes Sea&Sea’s MDX ports, and ships with a vacuum system, and there are a number of electronic and optical strobe triggering options available.

From Sea&Sea


Sea&Sea MDX-αU Underwater Housing for Sony α1/α9II/α7sIII/α7RIV/α7IV

Universal compatibility with the Sony Alpha series. The future-oriented mirrorless SLR compatible housing is now fully loaded

Universal design for the future. The back panel is designed to be large.

The back acrylic panel is more than twice as large as before to improve the visibility of the monitor and reduce the underwater weight. Furthermore, it is a sustainable design that can be used with new cameras in the future with minimal parts replacement.

Newly designed fiber-optic cable cover Newly designed optical fiber cable cover.

Newly designed fiber-optic cable cover included. Prevents optical cable terminals from falling out and smartly protects light-emitting panels and cable terminals. Includes a strap to prevent loss of the cover.

Leak Alarm Unit as standard equipment

The Leak Alarm Unit, which was previously available as an option, is now included as standard equipment. It is effective not only for early detection of underwater flooding accidents but also for the protection of equipment by checking its waterproof performance before entry. CR2032 lithium battery included.

Strobe Synchro System

Three optional strobe connection methods are available.

  1. Optical TTL connection
    [Product No.50139] Optical YS Converter S1

Compatible with SEA&SEA “Optical YS Converter S1” which converts the strobe light emission signal of the camera to LED light and synchronizes with the SEA&SEA YS strobe. It is a high-performance converter that does not just emit simple light-emitting signals, but also performs TTL auto light control. *Sony original adapter “ADP-MAA” is required separately for connecting camera and optical YS converter.

  1. Optical manual connection
    [Product No.50146] Manual flash trigger

For those who do not need TTL photography, the fiber-optic cable connection enables manual firing of the YS strobe.

  1. Electrical connection
    [Product No.50147] Strobe connector/N
    [Product No.50122] Optional Sync Cord 2-pin Connector

YS strobes can be electrically connected with a sync cord.

Full range of standard equipment

Functional Limitations and Enhancement Customization Kit

Common to all models

α1/α9II camera

α7IV camera

[Product No.50148] α1 customize kit for MDX-αU
Compatible with drive mode dial/focus mode switching lever.

[Product No.50149] α9II Customize Kit for MDX-αU
Compatible with drive mode dial and focus mode selection lever.

[Product No.50150] α7IV Customize Kit for MDX-αU
Compatible with shooting mode selection lever.

MDX-αU Other Features

*Some vignetting occurs when the VF180 1.2x is mounted on the housing, the upper part of the camera’s viewfinder cannot be viewed due to vignetting
* Equipped with two sacrificial zinc diodes (one on the front case and the other on the rear) to prevent electrolysis damage
* Tripod screw mount is located on the center underside of the housing
* Equipped with under guard to protect from scratch


Body: corrosion-resistant aluminum alloy (machined)
Grip: corrosion-resistant die-cast aluminum alloy
Depth rating
100m / 330ft
Dimensions (WxHxD)
330 x 169 x 137 mm / 12.9 x 6.6 x 5.4 inches
Approx. 2,900g / 102.3oz (Housing only)

Port System Chart