Our new boat is in the water now and we're enjoying life aboard. I dropped my favourite bucket overboard yesterday - a lovely blue rubber one, unbreakable, supposed to last me a lifetime. Being rubber, it sank. I hoped I might be able to get it at low tide, but there is 4 metres of water under us even at low water.
We have a depth sounder on this boat, and we have had long debates about whether to callibrate it to show depth from the bottom of the keel, or from the surface. It will be interesting to have an instrument for measuring how close we are to going aground, although I don't know whether I'll really trust it.
Up until now I've used a plumb line. I trust a lump of lead and a piece of string more than an electronic screen wired to a gadget somewhere I can't see it on the bottom of the boat.
People smile at me wryly when I advocate using the lead to measure depth. There is a culture of gadgetry in sailing that means many people have cast aside old-fashioned things. But some sailers nod knowingly - a bit of string and a lump of lead can't go wrong and need no electricity.
When Pytheas was at sea of course, there was no option but to plumb the depths. That's all the justification I need.