Ikelite has recently announced the new DS51 to replace their popular DS50:
The Ikelite DS51 Substrobe replaces the DS50, which has been a favorite of underwater photographers the world over. In addition to incorporating all the same great features of the DS50, the DS51 provides a Manual Exposure Mode with six (6) manual power settings in one-half f-stop increments for precise illumination of subjects underwater.
In addition, their DS125 now comes with a NIMH battery pack, yielding an extra 100 full power flashes per charge. That’s excellent news!