Shutter speeds at certain depths

PuravidaUK wrote:

I'll be in the Galapagos hoping to shoot hammerheads and I understand the conditions can be quite tricky, and thus perhaps difficult to fiddle around with camera settings. I'm torn between the TG-6 on one hand, or just spending much less on a GoPro and reducing my photography expectations.

You really buried the lead in not putting this in your original post.   This is the part that matters most.   Exposure at 100ft/30m varies greatly based on water clarity, time of day, and sunnyness above, and well as the subject matter (black mantas or darker sharks versus silvery ones).

the dive spot you're really talking about is Landslide on Wolf Island.   Perhaps the most exhilerating/challenging spot I've encountered in > 800 dives.   I went to there with my wife in 2013 when she had but 60 dives.  We knew it was a bit aggressive, even by California standards, but it was 2 for 1!  But because of that level of experience, and the difficulty of some of the dives, I generally put my housed camera down and just carried the go pro tray.

Landslide is full of sharks - hammers, galapagos, reef, silky, and you're on ledges right near the edge of the island.  Current flow exceeded 4 knots at times.   You basically hug a rock and hang on.   Plan to shred a pair of gloves.  If you turn your head sideways, the current starts to tug at it.     The water can be turbid - when we released to go our safety stop, we could only see clearly 10-20 feet in any direction (other than to note there were sharks in every direction).  On one, we either got caught in a pretty strong downdraft or the poor viz lead us to mishandled our BC inflation on the blind open water safety stop.

So to cut to the chase, I wouldn't recommend a camera you don't know how to use without looking at menus, and wouldn't be distracted by the wearing of gloves.  And understand the impact of the extra drag lugging it around.   Don't make this your first trip with dual strobe arms.

On positive side - with the fast current, the sharks swimming against it often are moving very slowly, so you could get away with a longer exposure.   Video shooting will do pretty well-  not nearly the same challenge around exposure and precise composition.   It will probably tell a better story too.   The TG has 4k shooting.  The smaller sensor probably works against you for the stills.   It will do fine in other spots, like the iguanas.

Great photographers can get amazing shots there.   But unlike many locales, I think it's pretty tough for us vacation shooters to do the same.  As you appear to be a newer shooter, I'd suggest the gopro or tg options over a more substantial, most costly route.  And if you assess yourself to be a greener diver, or not as experienced with rougher cold water diving, then just the gopro.   Focus on the diving and the views, don't give that up in pursuit of a photo.