Sure, I don't think you can actually sprint while diving, but I still hit space a lot, that might contribute.
~~As for what was done that day - woke up, on the upper floor of the house. Went down, harvested crops and items from machines e.g. cheese, mayonnaise, the thing that makes scrap out of junk, etc. refilled a bunch of those, let the animals out, picked up the items they dropped, then auto travelled to the diving pier, went down to speak to theo, went back up to the teleport point and used it to get to merfolk kingdom. I didn't talk to anyone there, just went straight down, hitting space out of habit, tried to go back up when I realized that wasn't where I wanted to go, and wasn't able to. ~~
Not sure if that helps, but hopefully something will?