I really like the feeling of Oobleck, the way it flows/becomes a solid. When made right for a man, it has like a suction ability that feels fucking amazing on the dick. My plan is find a way to make enough to lie down in it and basically be able to be almost fully submerged, the problem I'm having is I don't want to use a inflatable pool because it's usually to wide, which makes things a bit more expensive and I'm trying to save money. However if I use a rigid container I won't have to worry about the pool breaking potentially but most of the rigid containers I've seen is not long enough or tall enough. So any suggestions, links, or anything related would be helpful.

Try an under-bed storage container- you can get some long, narrow ones.

Inflatable bathtub or barrel baths might do it, while being a little smaller than your typical pool.

Inflatable mattress, especially when under inflated, will sag under bodyweight and create a narrow deep pool when you lie in it. Combine this with an inflatable pool it can be a bit more budget friendly. Also you've got the option of wedging the pool in with furniture to make it narrower.

I've also seen oobleck effects done with custard powder (kid's TV shows)- so there may be some cheaper substances out there

Thanks for the idea of the inflatable pool and mattress that might be perfect for what I'm looking for, I already have a local supply company for the cornstarch and they are really cheap.