Turns out we now own one of those portable blowup spa pools.  https://portablespas.co.nz/products/tekapo-spa

It takes approx 1000L of water, so that going to be about a ton.

Apparently the intention was to put it on our downstairs deck, that is about a meter off the ground at its highest point.

The deck was professionally installed by the builder when the house was built.   The house is on poles.  The deck has bearers front and back, doubled up, where one of each is partially cut into the house poles, and both bearers bolted through.  See the pics.

Is a deck of this construction going to hold a spa pool weighing 1ton?  Or do they need special reinforcing?

I can upload different pics if required.