Web alarm clock for 2:43 p.m.
While you watch the time, the carabao can finish drinking before you take it back to the field for another stretch of ploughing. Set the alarm for 2:43 pm so the pause has a clear end rather than relying on repeated glances at the clock. That still leaves the afternoon work ready to resume well before 3:00 pm.
Keeping the alarm page behind another app can be handy while you check the weather or note which furrow comes next. A background tab may be slowed or suspended by the browser, however, so its alert can arrive late. More crucially, the carabao may drink longer than planned if you close the page or let the phone sleep, because this browser alarm cannot sound then. Leave the page open, keep the phone awake, and turn the volume up enough to hear it outdoors.
Once the carabao has been watered at 2:43 pm, avoid treating the remaining midday heat as a reason to stretch the pause into a nap. If you plan to sleep after the fieldwork, keep that rest for later and use this short break for shade, water, and checking the harness. That preserves the sleep you intended after the job instead of taking part of it now and returning to the plough feeling unsettled.