You have to decide what to do with this tub.

Boring holes could be a 2nd choice. Click on W on the A-Z (Goypedia) at the foot of this page then on 'water features and ideas'. You will find plenty of inspiration there. Do let us see what you decide to do with it. I am not sure if the tub will rot if you go for either a planter or a water feature. Maybe someone else can advise whether or not a liner would be a good idea to prolong its life.

I'm wondering how easy it wold be to keep the water fresh as there is only a small surface area compared with the depth. You'd need lots of oxygenaters in there - perhaps a good case for Canadian pondweed!

Just thinking now too about the old galvanised iron buckets we used before plastic ones. They always rusted through eventually so perhaps a tree might not be a good idea because it might be hard to transplant it when the tub gives up the ghost at it should be well grown by then.

Suppose you put another much shallower container supported inside it and grew rockery plants that would trail over the side?

How wold that work for drainage Stera? Would definitely need holes drilled and they are likely to rust more rapidly due to the water...

At the moment I have a handleless trug that fits snugly into the top supported by a lot of polystyrene to keep the weight manageable, Its filled with spring flowering bulbs at present. Only problem is that water drains through the trug and stagnates in the bottom and it needs to be tipped over to drain the water if we have heavy rain. But will have a look at the water feature area of this site. once I've drilled there's no going back . The tub itself is at least 70 years old but shows no signs of rust anywhere.

I would say that it's far too small for a water feature so you need to consider drilling holes in the bottom and growing something like a small bay tree/shrub or a Christmas box. If you are worried that your tub will rust when you drill holes; you could consider drilling maybe 2 or 3 holes in the sides at the bottom of the tub and supergluing around the edges to seal the holes from rusting.

There's your answer MG! Its going to rust eventually anyway.

If you're going to invest the time, money & energy in creating a water garden, definitely click on the 'w' on the "Goypedia page to see many clever ideas.