Pescatarian gets treated online as vegetarian-plus-fish, an afterthought bolted onto someone else's diet, when really it's built around a different protein source doing most of the heavy lifting. A pescatarian grocery list needs the shop to actually plan for that (salmon, tinned tuna, prawns, white fish), not just remove chicken and mince and hope things balance out.
The builder has pescatarian as its own diet preset, alongside vegetarian and vegan. Pick it, set your protein and calorie targets, and the free basket gets built with fish, seafood, eggs and dairy in the mix, plus the usual veg, grains and fats. Prioritise the ingredients you actually like, or rule out the ones you don't, and typical prices show roughly what it'll cost before you're anywhere near the till. Just try it — set pescatarian, set your targets, and let it build the list. A pescatarian week works when the fish is bought on purpose, not left as an afterthought.