Hi Mike. It's possible to go up the shannon estuary through Limerick city to the inland non-tidal shannon and 180nm north through the SEW waterway into the Erne system in Northern Ireland. The passage includes 4 giant loughs (Derg, Ree, Erne upper and Lower) and numberous smaller loughs. The for giant loughs are more like inland seas than lakes. Derg is 40km long by 16km wide. Generally boats of airdraft of upto 3.5m can do the whole system.