The Titan Mare Explorer (TiME) has already been under study for about two years. It is envisaged as a relatively low-cost endeavour – in the low $400m range.
It could launch in January 2016, and make some flybys of Earth and Jupiter to pick up the gravitational energy it would need to head straight at the Saturnian moon for a splash down in June 2023.
The scientists have a couple of seas in mind for their off-world maritime research vessel. Ligeia Mare and Kraken Mare are both about 500km across.
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Pictures will be essential, though. The Huygens lander sent back a vista of orange pebbles – one of the most iconic images in Solar System exploration history. A view from the surface of a methane lake, looking towards the shore would be just as amazing.