Learning Resources Under the Sea Shells Word Problem Activity Set. Help bring word problems to life with these colourful plastic clam shells and fun little crab and starfish counters! This under the sea themed set provides an engaging way to practise a variety of early maths skills including adding, subtracting and finding the missing number. Set includes 40 doublesided word problem cards, four plastic clam shells and 80 colourful plastic counters (40 crabs in two colours, 40 starfish in two colours). Clams measure 12cm L x 10cm W. Suitable for ages 6+