I have just purchased an Antlia oil free compressor, mainly for touch up jobs on my Roberts Spray, away from the marina.
These compressors haven't been out long and in Australia retail for $299, although I got 30% off last Saturday at Repco.
Model No AN20210F.

60L/min free air delivery, max pressure 115PSI, draws 550w so I can power it with a 1KVA Honda on board (or in the tinny). The compresor unit with tank and all fittings weighs 22kg, so it's quite manageable.
It is very quiet and works a little touch up gun, no worries.

My question: with the correct filters (open to suggestions), a 100PSI regulator and about 20m of dive hose, does anybody see this unit as a problem for diving to check the hull and clean the prop. The boat only draws 4'4", but I realise poor air and any operation, even at 5ft depth, does carry potential dangers. I previously (in the 80's, before licences came out) used scuba for commercial collection of saltwater aquarium fish in Queensland where I live.