In the following sentence, "Hurry, give me anything that will hold water!" What verb tense is "will hold" ? Not future simple, I presume.
You have only two possibilities: a) future simple - will as auxiliary verb b) will as modal verb such as can
As future tense makes no sense at all it can only be possibility b) and then the tense is present tense of "will".
The meaning is nothing but
1 something that holds water or
2 something that can hold water.
Due to the ambiguity of will + infinitive the use of "will" as a modal verb is somewhat limited, mostly to negative forms as in
As to your sentence above this use of "will" looks like the language of an earlier time or like individual or regional habit of speech.
As to your sentence above this use of "will" looks like language of an earlier time or an individual habit of speech or a regional variant of speech.
It is future simple.
An alternative construction would be
This would make sense and would be a simple present. Something that holds water now will also hold water in the foreseeable future.
Because the holding has not yet occurred, but will occur once the vessel is put into service,