A 17-year-old male from the Skegness area has been arrested in connection with serious assault in the town.
He has been released on bail pending further enquiries.
It follows an incident in the early hours of Sunday morning.
Officers said the incident took place in or near the Summerlands Pub on Roman Bank, Winthorpe, at around half past midnight.
A man, aged in his 40s, remains in hospital where he is receiving treatment for a head injury.
Officers said anyone drinking in, or leaving the Summerlands Pub may have vital information.
If you witnessed a fight or altercation, or you have any information that could assist officers with this enquiry you are asked to call 101 with information for the attention of PC1370 Evans or DC44 Graves at Skegness CID. Alternatively you can call the independent charity Crimestoppers on 0800 555 111.