The rescue I got my rats from said rats can swim and to put frozen peas in a baking tray with water and they'll go get them. Well this didn't go very well. While they wanted the peas they wouldn't go near the water. Does anybody have any other ideas.
I don't make mine swim for the peas, I just put them in a nice sturdy bowl with water that way they can stand on the edge of the bowl and "fish" them out with they front paws. They really seem to enjoy it. You can also do dig boxes with all kinds of things for them to find. I'll usually throw some treats on the bottom of a small bin and then cover them with enough aspen so that they have to dig for them.
Pea fishing is fun, but like kksrats said, with only a little water in the bowl. Some rats hate getting wet. Digging boxes are a lot of fun, you can use bedding or shredded paper. Tubes and tunnels are a favorite here, as well as anything they can climb. I haven't been able to find a whole lot of pre-made enrichment items for rats, but there are tons of things for ferrets, and those work well too.
Mine love boxes and nest-making. So I tape up a small box and cut holes in the sides, and then provide them with sheets of tissue paper (now in abundance since it was just Christmas) and let them go to town making a nice fluffy nest.
They also enjoy hazelnuts, pecans, almonds and walnuts in the shell, because it's a project getting the shell open!
I gave them some small pine cones last week and it looks like at least one of them had fun nibbling on that.