A scheme was backed by Rother District Council on Monday.
Cabinet gave its support to a Government initiative to allow groups free access to local authority pools - but warned their backing was dependent on adequate funding.
Rother decided to accept the Government's grant of £43,123 for 2009/10 to support free swimming for over 60s.
Pool contractors Freedom Leisure advised cabinet the likely cost would be around £45,000. Rother will pick up any shortfall.
They were also told free swimming for under 16s will cost in the region of £126,000. A grant figure has yet to be decided upon by Government and will only be accepted, by the director of services under delegated powers, if it meets at least 95 per cent of the total cost.
The scheme would also allow Rother to apply for capital funding for pool modernisation.
But cabinet warned the free swimming could only be temporary, as Government funding was only guaranteed for two financial years.
Beyond that, local authorities may have to foot the bill - something cabinet said Rother would be unlikely to do.
Portfolio holder Cllr Jonathan Johnson warned the extra financial burden would require an 'unsustainable' increase in council tax.
Opposition leader and non-cabinet member, Cllr Sue Prochak, also supported the scheme, but warned Rother could, "be in the invidious position as the misers who say they can't afford it. Because we won' be able to afford if after two years."
Other members feared Rother could be left to pick up a massive shortfall if Freedom Leisure fail to calculate the correct cost of the scheme.
Head of amenities Madeleine Gorman told members Rother would only pay up to the amount quoted by contractors. Any shortfall would be the responsibility of Freedom Leisure under the terms of their contract.
Councillors were also assured if Government funding did not cover at least 95 per cent of the cost of allowing under 16s to swim for free, the offer would not be accepted regardless.
Rother leader Cllr Carl Maynard said: "Clearly it is a shame that this is, if you like, a temporary scheme. I think it is important to emphasise the point made by Cllr Johnson about the capital gain opportunities - that cannot be underestimated.
"I think it is clearly a shame it cannot be guaranteed by central government this (the grant) will be more than two years, but also one has to optimistic of what it can offer to under 16s with childhood obesity, for example, and that has to be a good thing."