I watched some youtube videos about Duct Seal usage to mount transducer in-hull, they mostly used some Duct Seal Compound in the cube shape
Something similar to this:
https://www.homedepot.com/p/Ideal-1-lb- ... /300496860
Unfortunately, I can't find something like this in NZ. Any ideas would be appreciated? Maybe something instead of this?

Cheers,
Barac