There are 18 words that start with 'seal'.
| seal | seals | sealed | 
| sealer | sealant | sealers | 
| sealery | sealift | sealing | 
| sealable | sealants | sealifts | 
| seallike | sealskin | sealeries | 
| sealifted | sealskins | sealifting | 
Note: These 18 words that start with 'seal' are found from the USA & Canada version of the tournament Scrabble word list.