The SubSea 150 strobes used a throw away 510 V battery. The smaller slightly less expensive Subsea 100 (I had two) used a throw away 300V battery.
The batteries were quite expensive and you had no way to tell when it would die. Many of my fellow UW photographers used them hand held aiming with Nikonos cameras. I started in 1970 right after getting trained (pre-national certification days) and buying these batteries for a trip was always a financial stretch for us poor working stiffs.
David Doubilet of National Geographic and other emerging UW photographers chose these because of their wonderful warm soft powerful light output.
After many stumbles with reliability the Ikelite 150 / 300 and eventually 400 watt second strobes with a warm 4800K color temperature and circular flashtube became what many UW photographers migrated to.
Today strobe color temp isn't as important due to digital and post processing capability on your computer, tablet and even phone
Just one old geezer's opinion LOL......
David Haas
www.haasimages.com