Swimming near Tristan da Cunha

Hi all,Position: 37-04S 012-19W Tristan da CunhaCOG: at anchorSOG: 0.0KNETA Cape Town 28 APR 2023 LAMYesterday morning, we found ourselves anchored in front of Calshot Harbour with a good swell making the ship bounce up and in strange jerky motions. The swell here bounces back from the coast, causing interference with the arriving swell.We split the night watches so everyone could go ashore for a few hours in their off-watch time. The whole voyage crew spent the day ashore in conditions between agreeable but cloudy and agreeable for most and very wet.During the landing I had another look at the forecast and previous average speeds (between 6.4 and 8.2 knots) and decided that we could probably stay another day.Two hours before our intended pick-up time, the harbourmaster called that conditions in the harbour were worsening and I had to blow the horn to call everyone back to the ship. Apparently the horn could be heard all the way at the back of the potatoe patches and on board the echo was still sounding 30 seconds after.Afterwards there was a request to go for a swim. There didn't seem to be any current, so about 50% of the voyage crew went for a dip.