The connectors on the flash that you intend to purchase should obviously match those on the camera that it will be plugged into.
There is no standard for connectors on underwater strobes, although the old five pin Nikonos V plug and socket has survived and is still universal for TTLThrough The Lens. A term applied to viewfinders and metering systems that operate behind the lens. As such TTL is accurate because it sees what the lens sees. strobes.
Some types of lead can have connectors that can be unplugged underwater. This is an advantage should you wish to take two cameras but only one flash (or two strobes and one camera).
Many compactType of camera that does not employ a SLR viewfinder. digital compact underwater camera systems now employ an optical link. This is a fiber optic cable that takes the light from the built-in flash (in the camera) to the strobe. This system has the advantage of not needing to go through the housingA casing or box with waterproof seals designed to contain a camera or other equipment in such a way that it can be used underwater., always a potential problem area.
You need to cover the built-in flash in compact cameras properly because it can cause backscatterBackscatter is light reflected from suspended particles in the water a problem in underwater flash photography caused by having the flash too close to the camera lens..
Sealoc connectorAlso known as a Nelson connector. A 2 pin wet connector i.e. a connector which can be pulled out and plugged in underwater. Used for flash synchronization on the Sea & Sea Motormarine Mk1. Also used as a telephone connector on fullface diving masks.
Nikonos connectorA five or three pin U/W flash lead plug/socket system.
Sea and Sea connectorA 4 pin waterproof connector used with the Sea & Sea TTL flash system.
EO connectorElectro Oceanic A type of wetconnector with two contacts in appearance like a rubber jackplug.
ICS2A 2 pin wet connector used with early Ikelite manual flash units.
ICS5A 5 pin O-ring sealed connector used mainly with Ikelite TTL flash units and video lights.
BNC connectorBayonet Neill Concelman (named after the designers Paul Neill and Carl Concelman). Coaxial connector used for video ethernet and radio frequency signals.
Buccaneer connectorMultipole (multipin) waterproof connector manufactured by Bulgin with an ingress protection rating of IP68 1 bar (i.e. submersible to a depth of at least 10m and in practice a lot more).
ICS4An obsolete 4 pin O-ring sealed connector used with early Ikelite automatic flash units.
ICS10A 10 pin Oring sealed connector used with scientific and technical instrumentation.