Ah, so that's why they used steam in Voyage, I guess.
That, and probably the time and cost of cleaning up the water afterwards.
Voyage, over time, did everything they could to do these episodes as quickly and cheaply as possible. The rear projection in the observation nose was used less often in the color years, using a live “bubble in glass system” instead. Water on the standing sets became rare if not totally stopped (other than stock footage) and Irwin even stopped including women after the second season. The exception was one episode, “The Mermaid” which was built around movie (
Mermaids of Tiburon) and prior episode footage. The back half of the third season often had huge stock footage episodes (“No Escape from Death”), duplicates or brainwashed crew, stunt guys in costumes…or, as in "Shadowman," a sheet! I don’t have production schedules, but you can almost bet your mortgage that a lot of
Voyages in the late 3rd season were shot in 3 or 4 days and cost very little. So, with all that in mind, I totally get why water was no longer used to illustrate hull breaches.
It was a little surprising that Irwin poured a little more money into the series in the 4th year. I guess with
The Time Tunnel gone, he wanted to give his existing shows a better shot (
LIS got a nice revamp also). The series seemed a little brighter, as if they turned up the lights again. The new opening credits partway in were a wonderful touch and episodes like “Fires of Death” and “Journey With Fear,” while nonsense, were exciting simply because of the amount of money invested in the sets and effects.