Good hindsight.
If you find a waterproof case that works for the FZ300, please report on it, I, and I am sure others, would like to know about it.
Cheers!
I couldn’t find an FZ300 specific waterproof housing, but here is what I have found so far. They all claim to be used for diving, although with depth restrictions. If anyone has experience with these I would like to hear it. I think using it as a sort of deck bag that you can take photos with might be reasonable. I’m thinking the Dicapac unless the Outec is considered significantly better. I see I posted the wrong size Outex for the FZ300. It should be the medium if I remember the specs.
DiCAPac WP-S10 Waterproof Case WP-S10 B&H Photo Video (bhphotovideo.com)
Outex 100X Underwater Camera Cover (Small) COVER 100X B&H Photo (bhphotovideo.com)
Outex Front Glass for Underwater Camera Cover 82MM B&H Photo (bhphotovideo.com)
Ewa-Marine U-A100 Underwater Housing for DSLRs and EM U-A100 B&H (bhphotovideo.com)
This might be the better Dicapac case.