The Sea Slice is up for sale for a mere $180,000. A similar vessel could be useful for explorer-oriented Travellers, or for light military duties. It was launched in 1996 (about TL 8), so it would be interesting using it on low-tech worlds of sail and slave galleys. Or – if you are more daring – in a more World War II-style, TL 5 naval campaign.
This link has a nice selection of interior shots: it might be useful as a first-approximation of how a starship should look, if you are just another landlubber like me.