Discovery and Extensive Follow-Up of SN 2024ggi, a nearby type IIP supernova in NGC 3621

We present the discovery and early observations of the nearby Type II supernova (SN) 2024ggi in NGC 3621 at 6. 64 +/- 0. 3 Mpc. The SN was caught 5. 8 (+1. 9 -2. 9) hours after its explosion by the ATLAS survey. Early-phase, high-cadence, and multi-band photometric follow-up was performed by the Kinder (Kilonova Finder) project, collecting over 1000 photometric data points within a week. The combined o- and r-band light curves show a rapid rise of 3. 3 magnitudes in 13. 7 hours, much faster than SN 2023ixf (another recent, nearby, and well-observed SN II). Between 13. 8 and 18. 8 hours after explosion SN 2024ggi became bluer, with u-g colour dropping from 0. 53 to 0. 15 mag. The rapid blueward evolution indicates a wind shock breakout (SBO) scenario. No hour-long brightening expected for the SBO from a bare stellar surface was detected during our observations. The classification spectrum, taken 17 hours after the SN explosion, shows flash features of high-ionization species such as Balmer lines, He I, C III, and N III. Detailed light curve modeling reveals critical insights into the properties of the circumstellar material (CSM). Our favoured model has an explosion energy of 2 x 10⁵1 erg, a mass-loss rate of 10^-3 solarₘass/yr (with an assumed 10 km/s wind), and a confined CSM radius of 6 x 10¹4 cm. The corresponding CSM mass is 0. 4 solarₘass. Comparisons with SN 2023ixf highlight that SN 2024ggi has a smaller CSM density, resulting in a faster rise and fainter UV flux. The extensive dataset and the involvement of citizen astronomers underscore that a collaborative network is essential for SBO searches, leading to more precise and comprehensive SN characterizations.