I know this area very well; I used to keep my own boat in Beaumaris and I sailed a commercial vessel through the Menai straits many times (and as a student I lived in Penmon!)
The tide rips through the deep water between Anglesey and Puffin Island. Between Puffin Island and Conwy is a vast area of shallow sandbanks without much tide except in the Conwy river channel. North of Anglesey, where the search seems to be focussed, you are back into strong tides close inshore, fierce tidal races off Pt Lynas and Moelfre and deep water. So a complex area to search with many hazards and steep tide gradients which will make a search challenging because a mile or so difference in where and how he entered the water can make a huge difference in where the wreckage ends-up.