There are 8 11-letter words that start with 'sea'.
| seaborgiums | seamanships | seaminesses | 
| searchingly | searchlight | seasickness | 
| seasonality | seaworthier | |
Note: These 8 11-letter words that start with 'sea' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with seas, seam, seaw, sear, seat, seal, seab, seaf, seac, seap, sead, seag, seah, sean, seaq.
4-letter words start with 'sea' (5)