To You: a convenient way to carry your vegetables
To a seal: it looks like a jellyfish, gets eaten and could choke the seal or if the seal eats a lot of plastic bags, its gut will be so filled with plastic it has no room for real food and it will die.
To avoid this happening:
shop in shops that use paper produce bags
take along your own fabric produce bags
avoid using produce bags of any type, where possible
talk to the managers of the shops where you buy fruit and veg and get them to reduce their use of plastic, move to using cloth produce bags or at least paper.
reuse all plastic bags you get - this size of plastic bag for example is a perfect fit for our bedroom bin.
Paper bags are not entirely perfect, it needs possibly even more energy to make paper bags than to make plastic bags but sea creatures don't die from ingesting or becoming trapped in paper bags and as Yowlyy points out in the comments below, paper bags can usually be composted. Cloth bags, on the other hand, are very long lasting, you can see two of mine here.